G.f.: A(x,y) = (1-y)^2 * Sum_{n>=0} (2*n+1) * y^n * (1 + x*(1-y)^2 )^(n*(n+1)/2).

Terms

a(0) =1a(1) =1a(2) =0a(3) =3a(4) =3a(5) =0a(6) =0a(7) =0a(8) =15a(9) =15a(10) =0a(11) =0a(12) =0a(13) =0a(14) =5a(15) =100a(16) =100a(17) =5a(18) =0a(19) =0a(20) =0a(21) =0a(22) =0a(23) =105a(24) =840a(25) =840a(26) =105a(27) =0a(28) =0a(29) =0