a(n) equals the coefficient of x^n in Sum_{m>=0} (x^m + 1/x^m)^m for n > 0.

Terms

a(0) =1a(1) =0a(2) =3a(3) =1a(4) =10a(5) =0a(6) =35a(7) =4a(8) =127a(9) =0a(10) =462a(11) =15a(12) =1716a(13) =0a(14) =6440a(15) =57a(16) =24310a(17) =0a(18) =92378a(19) =210a(20) =352737a(21) =0a(22) =1352078a(23) =798a(24) =5200301a(25) =0a(26) =20058384a(27) =3003a(28) =77558760a(29) =0