G.f.: Product_{k>=1} 1/(1-(4*x)^k)^(k/2).

Terms

a(0) =1a(1) =2a(2) =22a(3) =148a(4) =1126a(5) =6780a(6) =49020a(7) =290664a(8) =1945734a(9) =11786988a(10) =74564884a(11) =445398168a(12) =2767974620a(13) =16299877464a(14) =98372647992a(15) =577710929872