a(n) = a(1)*a(n-1) + a(2)*a(n-2) + ...+ a(n-1)*a(1) for n >= 5, starting 1,1,1,0.

Terms

a(0) =1a(1) =1a(2) =1a(3) =0a(4) =2a(5) =5a(6) =14a(7) =42a(8) =122a(9) =360a(10) =1068a(11) =3181a(12) =9526a(13) =28654a(14) =86558a(15) =262528a(16) =799212a(17) =2441538a(18) =7483052a(19) =23004500a(20) =70921492a(21) =219226064a(22) =679328952a(23) =2109948221a(24) =6567539814a(25) =20483936790a(26) =64010196918a(27) =200382350016a(28) =628344541644