G.f.: 2*q * Product_{n>=1} (1 + q^(2*n))/((1 + q^n)*(1 + q^(2*n-1))*(1 + q^(4*n))) in powers of q.

Terms

a(0) =2a(1) =-4a(2) =6a(3) =-12a(4) =16a(5) =-24a(6) =38a(7) =-52a(8) =74a(9) =-104a(10) =142a(11) =-192a(12) =258a(13) =-340a(14) =446a(15) =-584a(16) =756a(17) =-972a(18) =1244a(19) =-1580a(20) =1996a(21) =-2516a(22) =3148a(23) =-3924a(24) =4878a(25) =-6032a(26) =7434a(27) =-9136a(28) =11182a(29) =-13644