| Step | Hyp | Ref
 | Expression | 
| 1 |   | id 19 | 
. . . . . 6
⊢ (𝑀 = 𝑁 → 𝑀 = 𝑁) | 
| 2 |   | fveq2 5558 | 
. . . . . 6
⊢ (𝑀 = 𝑁 → (𝐹‘𝑀) = (𝐹‘𝑁)) | 
| 3 | 1, 2 | opeq12d 3816 | 
. . . . 5
⊢ (𝑀 = 𝑁 → 〈𝑀, (𝐹‘𝑀)〉 = 〈𝑁, (𝐹‘𝑁)〉) | 
| 4 |   | freceq2 6451 | 
. . . . 5
⊢
(〈𝑀, (𝐹‘𝑀)〉 = 〈𝑁, (𝐹‘𝑁)〉 → frec((𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑀, (𝐹‘𝑀)〉) = frec((𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉)) | 
| 5 | 3, 4 | syl 14 | 
. . . 4
⊢ (𝑀 = 𝑁 → frec((𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑀, (𝐹‘𝑀)〉) = frec((𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉)) | 
| 6 |   | fveq2 5558 | 
. . . . . 6
⊢ (𝑀 = 𝑁 → (ℤ≥‘𝑀) =
(ℤ≥‘𝑁)) | 
| 7 |   | eqid 2196 | 
. . . . . 6
⊢ V =
V | 
| 8 |   | mpoeq12 5982 | 
. . . . . 6
⊢
(((ℤ≥‘𝑀) = (ℤ≥‘𝑁) ∧ V = V) → (𝑥 ∈
(ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉) = (𝑥 ∈ (ℤ≥‘𝑁), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉)) | 
| 9 | 6, 7, 8 | sylancl 413 | 
. . . . 5
⊢ (𝑀 = 𝑁 → (𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉) = (𝑥 ∈ (ℤ≥‘𝑁), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉)) | 
| 10 |   | freceq1 6450 | 
. . . . 5
⊢ ((𝑥 ∈
(ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉) = (𝑥 ∈ (ℤ≥‘𝑁), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉) → frec((𝑥 ∈
(ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉) = frec((𝑥 ∈ (ℤ≥‘𝑁), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉)) | 
| 11 | 9, 10 | syl 14 | 
. . . 4
⊢ (𝑀 = 𝑁 → frec((𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉) = frec((𝑥 ∈ (ℤ≥‘𝑁), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉)) | 
| 12 | 5, 11 | eqtrd 2229 | 
. . 3
⊢ (𝑀 = 𝑁 → frec((𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑀, (𝐹‘𝑀)〉) = frec((𝑥 ∈ (ℤ≥‘𝑁), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉)) | 
| 13 | 12 | rneqd 4895 | 
. 2
⊢ (𝑀 = 𝑁 → ran frec((𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑀, (𝐹‘𝑀)〉) = ran frec((𝑥 ∈ (ℤ≥‘𝑁), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉)) | 
| 14 |   | df-seqfrec 10540 | 
. 2
⊢ seq𝑀( + , 𝐹) = ran frec((𝑥 ∈ (ℤ≥‘𝑀), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑀, (𝐹‘𝑀)〉) | 
| 15 |   | df-seqfrec 10540 | 
. 2
⊢ seq𝑁( + , 𝐹) = ran frec((𝑥 ∈ (ℤ≥‘𝑁), 𝑦 ∈ V ↦ 〈(𝑥 + 1), (𝑦 + (𝐹‘(𝑥 + 1)))〉), 〈𝑁, (𝐹‘𝑁)〉) | 
| 16 | 13, 14, 15 | 3eqtr4g 2254 | 
1
⊢ (𝑀 = 𝑁 → seq𝑀( + , 𝐹) = seq𝑁( + , 𝐹)) |