3443712domain: NAppears in sequencesa(n) = 4*a(n-1) + 4*a(n-2), a(0)=1, a(1)=2.at n=10A084128Expansion of (1 + 6*x - 12*x^2 - 8*x^3)/(1 - 24*x^2 + 16*x^4).at n=10A164584a(1) = 1; for n > 1, a(n) = sigma((2^n)-1) - sigma((2^(n-1))-1), where sigma is A000203, the sum of divisors.at n=21A329890