6424120440domain: NAppears in sequencesa(n) = Sum_{k=0..n-1} {[x^k] A(x)^(n-k)} * {[x^(n-k-1)] A(x)^(k+1)} for n>0, with a(0)=1, where g.f. A(x) = Sum_{n>=0} a(n)*x^n.at n=12A161881