A025272 a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 5.

1, 1, 1, 2, 6, 17, 50, 150, 458, 1420, 4460, 14165, 45422, 146870, 478366, 1568076, 5169332, 17127466, 57005220, 190503772, 638986740, 2150472248, 7259433880, 24574658829, 83404648534, 283742556262, 967415888822, 3305124188428