212408191568domain: NAppears in sequencesa(n) = Sum_{k=0..2n-1} T(n,k) * T(n,k+1), with T given by A026519.at n=15A027263a(n) = Sum_{k=0..2n-1} T(n,k) * T(n,k+1), with T given by A026536.at n=15A027268