Dirichlet g.f.: zeta(2*s) / (zeta(s) * zeta(s-3)).

Terms

a(0) =1a(1) =-9a(2) =-28a(3) =9a(4) =-126a(5) =252a(6) =-344a(7) =-9a(8) =28a(9) =1134a(10) =-1332a(11) =-252a(12) =-2198a(13) =3096a(14) =3528a(15) =9a(16) =-4914a(17) =-252a(18) =-6860a(19) =-1134a(20) =9632a(21) =11988a(22) =-12168a(23) =252a(24) =126a(25) =19782a(26) =-28a(27) =-3096a(28) =-24390a(29) =-31752