558456domain: NAppears in sequencesa(n) = a(1)*a(n-1) + a(2)*a(n-2) + ... + a(n-3)*a(3) for n >= 4, with initial terms 2, -2, 1, 2.at n=21A025260a(n) = Sum_k k*A333274(n,k).at n=30A333276