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

Terms

a(0) =1a(1) =8a(2) =28a(3) =68a(4) =160a(5) =344a(6) =608a(7) =1032a(8) =1784a(9) =2836a(10) =4416a(11) =6928a(12) =10348a(13) =15260a(14) =21848a(15) =30112a(16) =42012a(17) =57312a(18) =76308a(19) =101272a(20) =131648a(21) =169064a(22) =215496a(23) =270344a(24) =335484a(25) =415128a(26) =506736a(27) =608908a(28) =738976a(29) =873268