| Step | Hyp | Ref | Expression | 
|---|
| 1 |  | df-1s 27871 | . . 3
⊢ 
1s = ({ 0s } |s ∅) | 
| 2 | 1 | fveq2i 6908 | . 2
⊢ ( bday ‘ 1s ) = (
bday ‘({ 0s } |s ∅)) | 
| 3 |  | 0sno 27872 | . . . . . . 7
⊢ 
0s ∈  No | 
| 4 |  | snelpwi 5447 | . . . . . . 7
⊢ (
0s ∈  No  → { 0s }
∈ 𝒫  No ) | 
| 5 | 3, 4 | ax-mp 5 | . . . . . 6
⊢ {
0s } ∈ 𝒫  No | 
| 6 |  | nulssgt 27844 | . . . . . 6
⊢ ({
0s } ∈ 𝒫  No  → {
0s } <<s ∅) | 
| 7 | 5, 6 | ax-mp 5 | . . . . 5
⊢ {
0s } <<s ∅ | 
| 8 |  | scutbdaybnd2 27862 | . . . . 5
⊢ ({
0s } <<s ∅ → ( bday
‘({ 0s } |s ∅)) ⊆ suc ∪ ( bday  “ ({
0s } ∪ ∅))) | 
| 9 | 7, 8 | ax-mp 5 | . . . 4
⊢ ( bday ‘({ 0s } |s ∅)) ⊆ suc
∪ ( bday  “ ({
0s } ∪ ∅)) | 
| 10 |  | un0 4393 | . . . . . . . . . 10
⊢ ({
0s } ∪ ∅) = { 0s } | 
| 11 | 10 | imaeq2i 6075 | . . . . . . . . 9
⊢ ( bday  “ ({ 0s } ∪ ∅)) =
( bday  “ { 0s
}) | 
| 12 |  | bdayfn 27819 | . . . . . . . . . 10
⊢  bday  Fn  No | 
| 13 |  | fnsnfv 6987 | . . . . . . . . . 10
⊢ (( bday  Fn  No  ∧
0s ∈  No ) → {( bday ‘ 0s )} = (
bday  “ { 0s })) | 
| 14 | 12, 3, 13 | mp2an 692 | . . . . . . . . 9
⊢ {( bday ‘ 0s )} = (
bday  “ { 0s }) | 
| 15 |  | bday0s 27874 | . . . . . . . . . 10
⊢ ( bday ‘ 0s ) = ∅ | 
| 16 | 15 | sneqi 4636 | . . . . . . . . 9
⊢ {( bday ‘ 0s )} =
{∅} | 
| 17 | 11, 14, 16 | 3eqtr2i 2770 | . . . . . . . 8
⊢ ( bday  “ ({ 0s } ∪ ∅)) =
{∅} | 
| 18 | 17 | unieqi 4918 | . . . . . . 7
⊢ ∪ ( bday  “ ({
0s } ∪ ∅)) = ∪
{∅} | 
| 19 |  | 0ex 5306 | . . . . . . . 8
⊢ ∅
∈ V | 
| 20 | 19 | unisn 4925 | . . . . . . 7
⊢ ∪ {∅} = ∅ | 
| 21 | 18, 20 | eqtri 2764 | . . . . . 6
⊢ ∪ ( bday  “ ({
0s } ∪ ∅)) = ∅ | 
| 22 |  | suceq 6449 | . . . . . 6
⊢ (∪ ( bday  “ ({
0s } ∪ ∅)) = ∅ → suc ∪ ( bday  “ ({
0s } ∪ ∅)) = suc ∅) | 
| 23 | 21, 22 | ax-mp 5 | . . . . 5
⊢ suc ∪ ( bday  “ ({
0s } ∪ ∅)) = suc ∅ | 
| 24 |  | df-1o 8507 | . . . . 5
⊢
1o = suc ∅ | 
| 25 | 23, 24 | eqtr4i 2767 | . . . 4
⊢ suc ∪ ( bday  “ ({
0s } ∪ ∅)) = 1o | 
| 26 | 9, 25 | sseqtri 4031 | . . 3
⊢ ( bday ‘({ 0s } |s ∅)) ⊆
1o | 
| 27 |  | ssrab2 4079 | . . . . . 6
⊢ {𝑥 ∈ 
No  ∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)} ⊆  No | 
| 28 |  | fnssintima 7383 | . . . . . 6
⊢ (( bday  Fn  No  ∧ {𝑥 ∈ 
No  ∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)} ⊆  No ) → (1o ⊆ ∩ ( bday  “ {𝑥 ∈ 
No  ∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)}) ↔ ∀𝑦 ∈ {𝑥 ∈  No 
∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)}1o ⊆
( bday ‘𝑦))) | 
| 29 | 12, 27, 28 | mp2an 692 | . . . . 5
⊢
(1o ⊆ ∩ ( bday  “ {𝑥 ∈  No 
∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)}) ↔ ∀𝑦 ∈ {𝑥 ∈  No 
∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)}1o ⊆
( bday ‘𝑦)) | 
| 30 |  | sneq 4635 | . . . . . . . . 9
⊢ (𝑥 = 𝑦 → {𝑥} = {𝑦}) | 
| 31 | 30 | breq2d 5154 | . . . . . . . 8
⊢ (𝑥 = 𝑦 → ({ 0s } <<s {𝑥} ↔ { 0s }
<<s {𝑦})) | 
| 32 | 30 | breq1d 5152 | . . . . . . . 8
⊢ (𝑥 = 𝑦 → ({𝑥} <<s ∅ ↔ {𝑦} <<s
∅)) | 
| 33 | 31, 32 | anbi12d 632 | . . . . . . 7
⊢ (𝑥 = 𝑦 → (({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅) ↔ ({ 0s
} <<s {𝑦} ∧
{𝑦} <<s
∅))) | 
| 34 | 33 | elrab 3691 | . . . . . 6
⊢ (𝑦 ∈ {𝑥 ∈  No 
∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)} ↔ (𝑦 ∈ 
No  ∧ ({ 0s } <<s {𝑦} ∧ {𝑦} <<s ∅))) | 
| 35 |  | sltirr 27792 | . . . . . . . . . . . . 13
⊢ (
0s ∈  No  → ¬
0s <s 0s ) | 
| 36 | 3, 35 | ax-mp 5 | . . . . . . . . . . . 12
⊢  ¬
0s <s 0s | 
| 37 |  | breq2 5146 | . . . . . . . . . . . 12
⊢ (𝑦 = 0s → (
0s <s 𝑦
↔ 0s <s 0s )) | 
| 38 | 36, 37 | mtbiri 327 | . . . . . . . . . . 11
⊢ (𝑦 = 0s → ¬
0s <s 𝑦) | 
| 39 | 38 | necon2ai 2969 | . . . . . . . . . 10
⊢ (
0s <s 𝑦
→ 𝑦 ≠ 0s
) | 
| 40 |  | bday0b 27876 | . . . . . . . . . . 11
⊢ (𝑦 ∈ 
No  → (( bday ‘𝑦) = ∅ ↔ 𝑦 = 0s
)) | 
| 41 | 40 | necon3bid 2984 | . . . . . . . . . 10
⊢ (𝑦 ∈ 
No  → (( bday ‘𝑦) ≠ ∅ ↔ 𝑦 ≠ 0s
)) | 
| 42 | 39, 41 | imbitrrid 246 | . . . . . . . . 9
⊢ (𝑦 ∈ 
No  → ( 0s <s 𝑦 → ( bday
‘𝑦) ≠
∅)) | 
| 43 |  | bdayelon 27822 | . . . . . . . . . . 11
⊢ ( bday ‘𝑦) ∈ On | 
| 44 | 43 | onordi 6494 | . . . . . . . . . 10
⊢ Ord
( bday ‘𝑦) | 
| 45 |  | ordge1n0 8533 | . . . . . . . . . 10
⊢ (Ord
( bday ‘𝑦) → (1o ⊆ ( bday ‘𝑦) ↔ ( bday
‘𝑦) ≠
∅)) | 
| 46 | 44, 45 | ax-mp 5 | . . . . . . . . 9
⊢
(1o ⊆ ( bday ‘𝑦) ↔ (
bday ‘𝑦) ≠
∅) | 
| 47 | 42, 46 | imbitrrdi 252 | . . . . . . . 8
⊢ (𝑦 ∈ 
No  → ( 0s <s 𝑦 → 1o ⊆ ( bday ‘𝑦))) | 
| 48 |  | ssltsep 27836 | . . . . . . . . 9
⊢ ({
0s } <<s {𝑦} → ∀𝑥 ∈ { 0s }∀𝑧 ∈ {𝑦}𝑥 <s 𝑧) | 
| 49 |  | vex 3483 | . . . . . . . . . . . 12
⊢ 𝑦 ∈ V | 
| 50 |  | breq2 5146 | . . . . . . . . . . . 12
⊢ (𝑧 = 𝑦 → (𝑥 <s 𝑧 ↔ 𝑥 <s 𝑦)) | 
| 51 | 49, 50 | ralsn 4680 | . . . . . . . . . . 11
⊢
(∀𝑧 ∈
{𝑦}𝑥 <s 𝑧 ↔ 𝑥 <s 𝑦) | 
| 52 | 51 | ralbii 3092 | . . . . . . . . . 10
⊢
(∀𝑥 ∈ {
0s }∀𝑧
∈ {𝑦}𝑥 <s 𝑧 ↔ ∀𝑥 ∈ { 0s }𝑥 <s 𝑦) | 
| 53 | 3 | elexi 3502 | . . . . . . . . . . 11
⊢ 
0s ∈ V | 
| 54 |  | breq1 5145 | . . . . . . . . . . 11
⊢ (𝑥 = 0s → (𝑥 <s 𝑦 ↔ 0s <s 𝑦)) | 
| 55 | 53, 54 | ralsn 4680 | . . . . . . . . . 10
⊢
(∀𝑥 ∈ {
0s }𝑥 <s
𝑦 ↔ 0s
<s 𝑦) | 
| 56 | 52, 55 | bitri 275 | . . . . . . . . 9
⊢
(∀𝑥 ∈ {
0s }∀𝑧
∈ {𝑦}𝑥 <s 𝑧 ↔ 0s <s 𝑦) | 
| 57 | 48, 56 | sylib 218 | . . . . . . . 8
⊢ ({
0s } <<s {𝑦} → 0s <s 𝑦) | 
| 58 | 47, 57 | impel 505 | . . . . . . 7
⊢ ((𝑦 ∈ 
No  ∧ { 0s } <<s {𝑦}) → 1o ⊆ ( bday ‘𝑦)) | 
| 59 | 58 | adantrr 717 | . . . . . 6
⊢ ((𝑦 ∈ 
No  ∧ ({ 0s } <<s {𝑦} ∧ {𝑦} <<s ∅)) → 1o
⊆ ( bday ‘𝑦)) | 
| 60 | 34, 59 | sylbi 217 | . . . . 5
⊢ (𝑦 ∈ {𝑥 ∈  No 
∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)} → 1o
⊆ ( bday ‘𝑦)) | 
| 61 | 29, 60 | mprgbir 3067 | . . . 4
⊢
1o ⊆ ∩ ( bday  “ {𝑥 ∈  No 
∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)}) | 
| 62 |  | scutbday 27850 | . . . . 5
⊢ ({
0s } <<s ∅ → ( bday
‘({ 0s } |s ∅)) = ∩
( bday  “ {𝑥 ∈  No 
∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)})) | 
| 63 | 7, 62 | ax-mp 5 | . . . 4
⊢ ( bday ‘({ 0s } |s ∅)) = ∩ ( bday  “ {𝑥 ∈ 
No  ∣ ({ 0s } <<s {𝑥} ∧ {𝑥} <<s ∅)}) | 
| 64 | 61, 63 | sseqtrri 4032 | . . 3
⊢
1o ⊆ ( bday ‘({
0s } |s ∅)) | 
| 65 | 26, 64 | eqssi 3999 | . 2
⊢ ( bday ‘({ 0s } |s ∅)) =
1o | 
| 66 | 2, 65 | eqtri 2764 | 1
⊢ ( bday ‘ 1s ) =
1o |