a[n]+a[n+2] = ∫{0,π/4} (tan(x))^n dx+∫{0,π/4} (tan(x))^(n+2) dx= ∫{0,π/4} (tan(x))^n·(1+tan²(x)) dx= ∫{0,π/4} (tan(x))^n·(1/cos²(x)) dx= ∫{0,π/4} (tan(x))^n·(tan(x))' dx= (tan(...