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

Terms

a(0) =1a(1) =3a(2) =2a(3) =7a(4) =-1a(5) =11a(6) =-3a(7) =15a(8) =-19a(9) =40a(10) =-34a(11) =23a(12) =-6a(13) =27a(14) =-76a(15) =141a(16) =-139a(17) =35a(18) =61a(19) =39a(20) =-270a(21) =358a(22) =-208a(23) =47a(24) =-35a(25) =106a(26) =-298a(27) =739a(28) =-874a(29) =59