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Theorem numclwwlk2 29367
Description: Statement 10 in [Huneke] p. 2: "If n > 1, then the number of closed n-walks v(0) ... v(n-2) v(n-1) v(n) from v = v(0) = v(n) ... with v(n-2) =/= v is k^(n-2) - f(n-2)." According to rusgrnumwlkg 28964, we have k^(n-2) different walks of length (n-2): v(0) ... v(n-2). From this number, the number of closed walks of length (n-2), which is f(n-2) per definition, must be subtracted, because for these walks v(n-2) =/= v(0) = v would hold. Because of the friendship condition, there is exactly one vertex v(n-1) which is a neighbor of v(n-2) as well as of v(n)=v=v(0), because v(n-2) and v(n)=v are different, so the number of walks v(0) ... v(n-2) is identical with the number of walks v(0) ... v(n), that means each (not closed) walk v(0) ... v(n-2) can be extended by two edges to a closed walk v(0) ... v(n)=v=v(0) in exactly one way. (Contributed by Alexander van der Vekens, 6-Oct-2018.) (Revised by AV, 31-May-2021.) (Revised by AV, 1-May-2022.)
Hypotheses
Ref Expression
numclwwlk.v 𝑉 = (Vtxβ€˜πΊ)
numclwwlk.q 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ β„• ↦ {𝑀 ∈ (𝑛 WWalksN 𝐺) ∣ ((π‘€β€˜0) = 𝑣 ∧ (lastSβ€˜π‘€) β‰  𝑣)})
numclwwlk.h 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ (β„€β‰₯β€˜2) ↦ {𝑀 ∈ (𝑣(ClWWalksNOnβ€˜πΊ)𝑛) ∣ (π‘€β€˜(𝑛 βˆ’ 2)) β‰  𝑣})
Assertion
Ref Expression
numclwwlk2 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (β™―β€˜(𝑋𝐻𝑁)) = ((𝐾↑(𝑁 βˆ’ 2)) βˆ’ (β™―β€˜(𝑋(ClWWalksNOnβ€˜πΊ)(𝑁 βˆ’ 2)))))
Distinct variable groups:   𝑛,𝐺,𝑣,𝑀   𝑛,𝑁,𝑣,𝑀   𝑛,𝑉,𝑣   𝑛,𝑋,𝑣,𝑀   𝑀,𝐾   𝑀,𝑉
Allowed substitution hints:   𝑄(𝑀,𝑣,𝑛)   𝐻(𝑀,𝑣,𝑛)   𝐾(𝑣,𝑛)

Proof of Theorem numclwwlk2
StepHypRef Expression
1 eluzelcn 12782 . . . . . . . 8 (𝑁 ∈ (β„€β‰₯β€˜3) β†’ 𝑁 ∈ β„‚)
2 2cnd 12238 . . . . . . . 8 (𝑁 ∈ (β„€β‰₯β€˜3) β†’ 2 ∈ β„‚)
31, 2npcand 11523 . . . . . . 7 (𝑁 ∈ (β„€β‰₯β€˜3) β†’ ((𝑁 βˆ’ 2) + 2) = 𝑁)
43eqcomd 2743 . . . . . 6 (𝑁 ∈ (β„€β‰₯β€˜3) β†’ 𝑁 = ((𝑁 βˆ’ 2) + 2))
543ad2ant3 1136 . . . . 5 ((𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3)) β†’ 𝑁 = ((𝑁 βˆ’ 2) + 2))
65adantl 483 . . . 4 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ 𝑁 = ((𝑁 βˆ’ 2) + 2))
76oveq2d 7378 . . 3 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (𝑋𝐻𝑁) = (𝑋𝐻((𝑁 βˆ’ 2) + 2)))
87fveq2d 6851 . 2 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (β™―β€˜(𝑋𝐻𝑁)) = (β™―β€˜(𝑋𝐻((𝑁 βˆ’ 2) + 2))))
9 simplr 768 . . 3 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ 𝐺 ∈ FriendGraph )
10 simpr2 1196 . . 3 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ 𝑋 ∈ 𝑉)
11 uz3m2nn 12823 . . . . 5 (𝑁 ∈ (β„€β‰₯β€˜3) β†’ (𝑁 βˆ’ 2) ∈ β„•)
12113ad2ant3 1136 . . . 4 ((𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3)) β†’ (𝑁 βˆ’ 2) ∈ β„•)
1312adantl 483 . . 3 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (𝑁 βˆ’ 2) ∈ β„•)
14 numclwwlk.v . . . 4 𝑉 = (Vtxβ€˜πΊ)
15 numclwwlk.q . . . 4 𝑄 = (𝑣 ∈ 𝑉, 𝑛 ∈ β„• ↦ {𝑀 ∈ (𝑛 WWalksN 𝐺) ∣ ((π‘€β€˜0) = 𝑣 ∧ (lastSβ€˜π‘€) β‰  𝑣)})
16 numclwwlk.h . . . 4 𝐻 = (𝑣 ∈ 𝑉, 𝑛 ∈ (β„€β‰₯β€˜2) ↦ {𝑀 ∈ (𝑣(ClWWalksNOnβ€˜πΊ)𝑛) ∣ (π‘€β€˜(𝑛 βˆ’ 2)) β‰  𝑣})
1714, 15, 16numclwwlk2lem3 29366 . . 3 ((𝐺 ∈ FriendGraph ∧ 𝑋 ∈ 𝑉 ∧ (𝑁 βˆ’ 2) ∈ β„•) β†’ (β™―β€˜(𝑋𝑄(𝑁 βˆ’ 2))) = (β™―β€˜(𝑋𝐻((𝑁 βˆ’ 2) + 2))))
189, 10, 13, 17syl3anc 1372 . 2 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (β™―β€˜(𝑋𝑄(𝑁 βˆ’ 2))) = (β™―β€˜(𝑋𝐻((𝑁 βˆ’ 2) + 2))))
19 simpl 484 . . . 4 ((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) β†’ 𝐺 RegUSGraph 𝐾)
20 simp1 1137 . . . 4 ((𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3)) β†’ 𝑉 ∈ Fin)
2119, 20anim12i 614 . . 3 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (𝐺 RegUSGraph 𝐾 ∧ 𝑉 ∈ Fin))
2211anim2i 618 . . . . 5 ((𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3)) β†’ (𝑋 ∈ 𝑉 ∧ (𝑁 βˆ’ 2) ∈ β„•))
23223adant1 1131 . . . 4 ((𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3)) β†’ (𝑋 ∈ 𝑉 ∧ (𝑁 βˆ’ 2) ∈ β„•))
2423adantl 483 . . 3 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (𝑋 ∈ 𝑉 ∧ (𝑁 βˆ’ 2) ∈ β„•))
2514, 15numclwwlkqhash 29361 . . 3 (((𝐺 RegUSGraph 𝐾 ∧ 𝑉 ∈ Fin) ∧ (𝑋 ∈ 𝑉 ∧ (𝑁 βˆ’ 2) ∈ β„•)) β†’ (β™―β€˜(𝑋𝑄(𝑁 βˆ’ 2))) = ((𝐾↑(𝑁 βˆ’ 2)) βˆ’ (β™―β€˜(𝑋(ClWWalksNOnβ€˜πΊ)(𝑁 βˆ’ 2)))))
2621, 24, 25syl2anc 585 . 2 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (β™―β€˜(𝑋𝑄(𝑁 βˆ’ 2))) = ((𝐾↑(𝑁 βˆ’ 2)) βˆ’ (β™―β€˜(𝑋(ClWWalksNOnβ€˜πΊ)(𝑁 βˆ’ 2)))))
278, 18, 263eqtr2d 2783 1 (((𝐺 RegUSGraph 𝐾 ∧ 𝐺 ∈ FriendGraph ) ∧ (𝑉 ∈ Fin ∧ 𝑋 ∈ 𝑉 ∧ 𝑁 ∈ (β„€β‰₯β€˜3))) β†’ (β™―β€˜(𝑋𝐻𝑁)) = ((𝐾↑(𝑁 βˆ’ 2)) βˆ’ (β™―β€˜(𝑋(ClWWalksNOnβ€˜πΊ)(𝑁 βˆ’ 2)))))
Colors of variables: wff setvar class
Syntax hints:   β†’ wi 4   ∧ wa 397   ∧ w3a 1088   = wceq 1542   ∈ wcel 2107   β‰  wne 2944  {crab 3410   class class class wbr 5110  β€˜cfv 6501  (class class class)co 7362   ∈ cmpo 7364  Fincfn 8890  0cc0 11058   + caddc 11061   βˆ’ cmin 11392  β„•cn 12160  2c2 12215  3c3 12216  β„€β‰₯cuz 12770  β†‘cexp 13974  β™―chash 14237  lastSclsw 14457  Vtxcvtx 27989   RegUSGraph crusgr 28546   WWalksN cwwlksn 28813  ClWWalksNOncclwwlknon 29073   FriendGraph cfrgr 29244
This theorem was proved from axioms:  ax-mp 5  ax-1 6  ax-2 7  ax-3 8  ax-gen 1798  ax-4 1812  ax-5 1914  ax-6 1972  ax-7 2012  ax-8 2109  ax-9 2117  ax-10 2138  ax-11 2155  ax-12 2172  ax-ext 2708  ax-rep 5247  ax-sep 5261  ax-nul 5268  ax-pow 5325  ax-pr 5389  ax-un 7677  ax-inf2 9584  ax-cnex 11114  ax-resscn 11115  ax-1cn 11116  ax-icn 11117  ax-addcl 11118  ax-addrcl 11119  ax-mulcl 11120  ax-mulrcl 11121  ax-mulcom 11122  ax-addass 11123  ax-mulass 11124  ax-distr 11125  ax-i2m1 11126  ax-1ne0 11127  ax-1rid 11128  ax-rnegex 11129  ax-rrecex 11130  ax-cnre 11131  ax-pre-lttri 11132  ax-pre-lttrn 11133  ax-pre-ltadd 11134  ax-pre-mulgt0 11135  ax-pre-sup 11136
This theorem depends on definitions:  df-bi 206  df-an 398  df-or 847  df-3or 1089  df-3an 1090  df-tru 1545  df-fal 1555  df-ex 1783  df-nf 1787  df-sb 2069  df-mo 2539  df-eu 2568  df-clab 2715  df-cleq 2729  df-clel 2815  df-nfc 2890  df-ne 2945  df-nel 3051  df-ral 3066  df-rex 3075  df-rmo 3356  df-reu 3357  df-rab 3411  df-v 3450  df-sbc 3745  df-csb 3861  df-dif 3918  df-un 3920  df-in 3922  df-ss 3932  df-pss 3934  df-nul 4288  df-if 4492  df-pw 4567  df-sn 4592  df-pr 4594  df-op 4598  df-uni 4871  df-int 4913  df-iun 4961  df-disj 5076  df-br 5111  df-opab 5173  df-mpt 5194  df-tr 5228  df-id 5536  df-eprel 5542  df-po 5550  df-so 5551  df-fr 5593  df-se 5594  df-we 5595  df-xp 5644  df-rel 5645  df-cnv 5646  df-co 5647  df-dm 5648  df-rn 5649  df-res 5650  df-ima 5651  df-pred 6258  df-ord 6325  df-on 6326  df-lim 6327  df-suc 6328  df-iota 6453  df-fun 6503  df-fn 6504  df-f 6505  df-f1 6506  df-fo 6507  df-f1o 6508  df-fv 6509  df-isom 6510  df-riota 7318  df-ov 7365  df-oprab 7366  df-mpo 7367  df-om 7808  df-1st 7926  df-2nd 7927  df-frecs 8217  df-wrecs 8248  df-recs 8322  df-rdg 8361  df-1o 8417  df-2o 8418  df-oadd 8421  df-er 8655  df-map 8774  df-pm 8775  df-en 8891  df-dom 8892  df-sdom 8893  df-fin 8894  df-sup 9385  df-oi 9453  df-dju 9844  df-card 9882  df-pnf 11198  df-mnf 11199  df-xr 11200  df-ltxr 11201  df-le 11202  df-sub 11394  df-neg 11395  df-div 11820  df-nn 12161  df-2 12223  df-3 12224  df-n0 12421  df-xnn0 12493  df-z 12507  df-uz 12771  df-rp 12923  df-xadd 13041  df-fz 13432  df-fzo 13575  df-seq 13914  df-exp 13975  df-hash 14238  df-word 14410  df-lsw 14458  df-concat 14466  df-s1 14491  df-substr 14536  df-pfx 14566  df-cj 14991  df-re 14992  df-im 14993  df-sqrt 15127  df-abs 15128  df-clim 15377  df-sum 15578  df-vtx 27991  df-iedg 27992  df-edg 28041  df-uhgr 28051  df-ushgr 28052  df-upgr 28075  df-umgr 28076  df-uspgr 28143  df-usgr 28144  df-fusgr 28307  df-nbgr 28323  df-vtxdg 28456  df-rgr 28547  df-rusgr 28548  df-wwlks 28817  df-wwlksn 28818  df-wwlksnon 28819  df-clwwlk 28968  df-clwwlkn 29011  df-clwwlknon 29074  df-frgr 29245
This theorem is referenced by:  numclwwlk3  29371
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