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

Terms

a(0) =1a(1) =0a(2) =1a(3) =0a(4) =1a(5) =1a(6) =0a(7) =0a(8) =4a(9) =1a(10) =0a(11) =0a(12) =3a(13) =11a(14) =1a(15) =0a(16) =0a(17) =0a(18) =27a(19) =26a(20) =1a(21) =0a(22) =0a(23) =0a(24) =17a(25) =148a(26) =57a(27) =1a(28) =0a(29) =0