| binom_coef(2 * i, i) * 2 * i < 4 ^ i, 0 < i ⊦ |
⊦ 0 ≤ j → (i + i0) ^ j = Σ countFun(0, j, λ j0. binom_coef(j, j0) * i ^ j0 * i0 ^ (j - j0))
0 ≤ 2 * i → (1 + 1) ^ (2 * i) = Σ countFun(0, 2 * i, λ j0. binom_coef(2 * i, j0) * 1 ^ j0 * 1 ^ (2 * i - j0)), binom_coef(2 * i, i) * 2 * i < 4 ^ i, 0 < i ⊦
Used terms: 2 * i, 1, 1