G.f. = Phi^6, where Phi = g.f. for A028930.

Terms

a(0) =1a(1) =0a(2) =12a(3) =12a(4) =72a(5) =120a(6) =352a(7) =600a(8) =1392a(9) =2212a(10) =4272a(11) =6480a(12) =10868a(13) =15396a(14) =23784a(15) =31712a(16) =45708a(17) =59184a(18) =81172a(19) =101928a(20) =136752a(21) =167864a(22) =218712a(23) =266112a(24) =339364a(25) =403680a(26) =509664a(27) =597060a(28) =736416a(29) =856236