a(n) = [(x*y)^n] Product_{k>=1} (1 + x^k + y^k)^k.

Terms

a(0) =1a(1) =0a(2) =2a(3) =18a(4) =50a(5) =190a(6) =536a(7) =1644a(8) =4432a(9) =12876a(10) =33560a(11) =89118a(12) =227734a(13) =572578a(14) =1409602a(15) =3424996a(16) =8150818a(17) =19152532a(18) =44455758a(19) =101565172a(20) =229712612a(21) =513207144a(22) =1134650028a(23) =2481664146a(24) =5379539720a(25) =11545719858a(26) =24574548632a(27) =51855844492a(28) =108559596182