G.f. = Phi^4*F^2, where Phi = g.f. for A028930, F = g.f. for A028959.

Terms

a(0) =1a(1) =4a(2) =12a(3) =40a(4) =100a(5) =216a(6) =472a(7) =896a(8) =1580a(9) =2732a(10) =4408a(11) =6816a(12) =10400a(13) =15280a(14) =22000a(15) =31088a(16) =43308a(17) =58072a(18) =78804a(19) =102176a(20) =134056a(21) =169408a(22) =218320a(23) =268228a(24) =339768a(25) =409244a(26) =507744a(27) =603368a(28) =738000a(29) =859424