have hlt : 0 < 2 := by decide
case succ
j : ℕ
ih : sum (fun i => i + i / 2 + 1) (j + j) = 3 * (j * j + j) + 1
⊢ sum (fun i => i + i / 2 + 1) (Nat.succ j + Nat.succ j) = 3 * (Nat.succ j * Nat.succ j + Nat.succ j) + 1
case succ
j : ℕ
ih : sum (fun i => i + i / 2 + 1) (j + j) = 3 * (j * j + j) + 1
hlt : 0 < 2
⊢ sum (fun i => i + i / 2 + 1) (Nat.succ j + Nat.succ j) = 3 * (Nat.succ j * Nat.succ j + Nat.succ j) + 1