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

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =0a(5) =0a(6) =6a(7) =6a(8) =0a(9) =0a(10) =0a(11) =4a(12) =56a(13) =56a(14) =4a(15) =0a(16) =0a(17) =0a(18) =1a(19) =117a(20) =722a(21) =722a(22) =117a(23) =1a(24) =0a(25) =0a(26) =0a(27) =0a(28) =126a(29) =2982