A025263 a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 4.

1, 2, 1, 6, 16, 57, 190, 676, 2418, 8860, 32848, 123413, 468246, 1792700, 6915438, 26856116, 104908160, 411944698, 1625120364, 6437911432, 25600033700, 102145852536, 408840420704, 1641061732941, 6604395207782, 26643368509676