39722domain: NAppears in sequencesa(n) = a(n-1)*(2n-1) + 2n with a(0)=0.at n=6A093303Number of secondary structures of size n with no stacks of length >=2.at n=16A202850a(0) = 0. If n is odd, a(n) = a(n-1) * n, otherwise a(n) = a(n-1) + n.at n=12A222559Expansion of Sum_{k>=0} k! * ( x * (1-x^3) )^k.at n=8A370508