| Step | Hyp | Ref
 | Expression | 
| 1 |   | df-ihash 10868 | 
. . . . 5
⊢ ♯ =
((frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0) ∪
{〈ω, +∞〉}) ∘ (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})) | 
| 2 | 1 | fveq1i 5559 | 
. . . 4
⊢
(♯‘𝐴) =
(((frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0) ∪
{〈ω, +∞〉}) ∘ (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}))‘𝐴) | 
| 3 |   | funmpt 5296 | 
. . . . 5
⊢ Fun
(𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}) | 
| 4 |   | funrel 5275 | 
. . . . . . 7
⊢ (Fun
(𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}) → Rel (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})) | 
| 5 | 3, 4 | ax-mp 5 | 
. . . . . 6
⊢ Rel
(𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}) | 
| 6 |   | peano1 4630 | 
. . . . . . 7
⊢ ∅
∈ ω | 
| 7 |   | reldom 6804 | 
. . . . . . . . . 10
⊢ Rel
≼ | 
| 8 | 7 | brrelex2i 4707 | 
. . . . . . . . 9
⊢ (ω
≼ 𝐴 → 𝐴 ∈ V) | 
| 9 |   | hashinfuni 10869 | 
. . . . . . . . . 10
⊢ (ω
≼ 𝐴 → ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝐴} = ω) | 
| 10 |   | omex 4629 | 
. . . . . . . . . 10
⊢ ω
∈ V | 
| 11 | 9, 10 | eqeltrdi 2287 | 
. . . . . . . . 9
⊢ (ω
≼ 𝐴 → ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝐴} ∈ V) | 
| 12 |   | breq2 4037 | 
. . . . . . . . . . . 12
⊢ (𝑥 = 𝐴 → (𝑦 ≼ 𝑥 ↔ 𝑦 ≼ 𝐴)) | 
| 13 | 12 | rabbidv 2752 | 
. . . . . . . . . . 11
⊢ (𝑥 = 𝐴 → {𝑦 ∈ (ω ∪ {ω}) ∣
𝑦 ≼ 𝑥} = {𝑦 ∈ (ω ∪ {ω}) ∣
𝑦 ≼ 𝐴}) | 
| 14 | 13 | unieqd 3850 | 
. . . . . . . . . 10
⊢ (𝑥 = 𝐴 → ∪ {𝑦 ∈ (ω ∪
{ω}) ∣ 𝑦
≼ 𝑥} = ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝐴}) | 
| 15 |   | eqid 2196 | 
. . . . . . . . . 10
⊢ (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}) = (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}) | 
| 16 | 14, 15 | fvmptg 5637 | 
. . . . . . . . 9
⊢ ((𝐴 ∈ V ∧ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝐴} ∈ V) → ((𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})‘𝐴) = ∪ {𝑦 ∈ (ω ∪
{ω}) ∣ 𝑦
≼ 𝐴}) | 
| 17 | 8, 11, 16 | syl2anc 411 | 
. . . . . . . 8
⊢ (ω
≼ 𝐴 → ((𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})‘𝐴) = ∪ {𝑦 ∈ (ω ∪
{ω}) ∣ 𝑦
≼ 𝐴}) | 
| 18 | 17, 9 | eqtrd 2229 | 
. . . . . . 7
⊢ (ω
≼ 𝐴 → ((𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})‘𝐴) = ω) | 
| 19 | 6, 18 | eleqtrrid 2286 | 
. . . . . 6
⊢ (ω
≼ 𝐴 → ∅
∈ ((𝑥 ∈ V ↦
∪ {𝑦 ∈ (ω ∪ {ω}) ∣
𝑦 ≼ 𝑥})‘𝐴)) | 
| 20 |   | relelfvdm 5590 | 
. . . . . 6
⊢ ((Rel
(𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}) ∧ ∅ ∈ ((𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})‘𝐴)) → 𝐴 ∈ dom (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})) | 
| 21 | 5, 19, 20 | sylancr 414 | 
. . . . 5
⊢ (ω
≼ 𝐴 → 𝐴 ∈ dom (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})) | 
| 22 |   | fvco 5631 | 
. . . . 5
⊢ ((Fun
(𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}) ∧ 𝐴 ∈ dom (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})) → (((frec((𝑥 ∈ ℤ ↦ (𝑥 + 1)), 0) ∪ {〈ω,
+∞〉}) ∘ (𝑥
∈ V ↦ ∪ {𝑦 ∈ (ω ∪ {ω}) ∣
𝑦 ≼ 𝑥}))‘𝐴) = ((frec((𝑥 ∈ ℤ ↦ (𝑥 + 1)), 0) ∪ {〈ω,
+∞〉})‘((𝑥
∈ V ↦ ∪ {𝑦 ∈ (ω ∪ {ω}) ∣
𝑦 ≼ 𝑥})‘𝐴))) | 
| 23 | 3, 21, 22 | sylancr 414 | 
. . . 4
⊢ (ω
≼ 𝐴 →
(((frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0) ∪
{〈ω, +∞〉}) ∘ (𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥}))‘𝐴) = ((frec((𝑥 ∈ ℤ ↦ (𝑥 + 1)), 0) ∪ {〈ω,
+∞〉})‘((𝑥
∈ V ↦ ∪ {𝑦 ∈ (ω ∪ {ω}) ∣
𝑦 ≼ 𝑥})‘𝐴))) | 
| 24 | 2, 23 | eqtrid 2241 | 
. . 3
⊢ (ω
≼ 𝐴 →
(♯‘𝐴) =
((frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0) ∪
{〈ω, +∞〉})‘((𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})‘𝐴))) | 
| 25 | 18 | fveq2d 5562 | 
. . 3
⊢ (ω
≼ 𝐴 →
((frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0) ∪
{〈ω, +∞〉})‘((𝑥 ∈ V ↦ ∪ {𝑦
∈ (ω ∪ {ω}) ∣ 𝑦 ≼ 𝑥})‘𝐴)) = ((frec((𝑥 ∈ ℤ ↦ (𝑥 + 1)), 0) ∪ {〈ω,
+∞〉})‘ω)) | 
| 26 | 24, 25 | eqtrd 2229 | 
. 2
⊢ (ω
≼ 𝐴 →
(♯‘𝐴) =
((frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0) ∪
{〈ω, +∞〉})‘ω)) | 
| 27 |   | pnfxr 8079 | 
. . 3
⊢ +∞
∈ ℝ* | 
| 28 |   | ordom 4643 | 
. . . . 5
⊢ Ord
ω | 
| 29 |   | ordirr 4578 | 
. . . . 5
⊢ (Ord
ω → ¬ ω ∈ ω) | 
| 30 | 28, 29 | ax-mp 5 | 
. . . 4
⊢  ¬
ω ∈ ω | 
| 31 |   | zex 9335 | 
. . . . . . . . . 10
⊢ ℤ
∈ V | 
| 32 | 31 | mptex 5788 | 
. . . . . . . . 9
⊢ (𝑥 ∈ ℤ ↦ (𝑥 + 1)) ∈ V | 
| 33 |   | vex 2766 | 
. . . . . . . . 9
⊢ 𝑧 ∈ V | 
| 34 | 32, 33 | fvex 5578 | 
. . . . . . . 8
⊢ ((𝑥 ∈ ℤ ↦ (𝑥 + 1))‘𝑧) ∈ V | 
| 35 | 34 | ax-gen 1463 | 
. . . . . . 7
⊢
∀𝑧((𝑥 ∈ ℤ ↦ (𝑥 + 1))‘𝑧) ∈ V | 
| 36 |   | 0z 9337 | 
. . . . . . 7
⊢ 0 ∈
ℤ | 
| 37 |   | frecfnom 6459 | 
. . . . . . 7
⊢
((∀𝑧((𝑥 ∈ ℤ ↦ (𝑥 + 1))‘𝑧) ∈ V ∧ 0 ∈ ℤ) →
frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0) Fn
ω) | 
| 38 | 35, 36, 37 | mp2an 426 | 
. . . . . 6
⊢
frec((𝑥 ∈
ℤ ↦ (𝑥 + 1)),
0) Fn ω | 
| 39 |   | fndm 5357 | 
. . . . . 6
⊢
(frec((𝑥 ∈
ℤ ↦ (𝑥 + 1)),
0) Fn ω → dom frec((𝑥 ∈ ℤ ↦ (𝑥 + 1)), 0) = ω) | 
| 40 | 38, 39 | ax-mp 5 | 
. . . . 5
⊢ dom
frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0) =
ω | 
| 41 | 40 | eleq2i 2263 | 
. . . 4
⊢ (ω
∈ dom frec((𝑥 ∈
ℤ ↦ (𝑥 + 1)),
0) ↔ ω ∈ ω) | 
| 42 | 30, 41 | mtbir 672 | 
. . 3
⊢  ¬
ω ∈ dom frec((𝑥
∈ ℤ ↦ (𝑥 +
1)), 0) | 
| 43 |   | fsnunfv 5763 | 
. . 3
⊢ ((ω
∈ V ∧ +∞ ∈ ℝ* ∧ ¬ ω ∈
dom frec((𝑥 ∈ ℤ
↦ (𝑥 + 1)), 0))
→ ((frec((𝑥 ∈
ℤ ↦ (𝑥 + 1)),
0) ∪ {〈ω, +∞〉})‘ω) =
+∞) | 
| 44 | 10, 27, 42, 43 | mp3an 1348 | 
. 2
⊢
((frec((𝑥 ∈
ℤ ↦ (𝑥 + 1)),
0) ∪ {〈ω, +∞〉})‘ω) =
+∞ | 
| 45 | 26, 44 | eqtrdi 2245 | 
1
⊢ (ω
≼ 𝐴 →
(♯‘𝐴) =
+∞) |