G.f. -x*(x-1)*(1+x)/(1-x-12*x^2-x^3+x^4).

Terms

a(0) =0a(1) =1a(2) =1a(3) =12a(4) =25a(5) =169a(6) =480a(7) =2521a(8) =8425a(9) =38988a(10) =142129a(11) =615889a(12) =2352000a(13) =9845809a(14) =38543569a(15) =158429388a(16) =628446025a(17) =2558296441a(18) =10219534560a(19) =41389108489a(20) =165953373625a(21) =670283913612