304543085040domain: NAppears in sequencesa(n) = Sum_{k=0..n-3} T(n,k) * T(n,k+3), with T given by A026374.at n=15A026949a(n) = Sum_{k=0..n} binomial(n+3,k+3) * binomial(2*k+6,k+6).at n=15A387239