G.f. is the polynomial (Product_{k=1..24} (1 - x^(3*k)))/(1-x)^24.

Terms

a(0) =1a(1) =24a(2) =300a(3) =2599a(4) =17526a(5) =97980a(6) =472419a(7) =2018226a(8) =7790145a(9) =27571180a(10) =90507690a(11) =278110755a(12) =805927980a(13) =2216192760a(14) =5813100315a(15) =14608785961a(16) =35307910374a(17) =82339194540a(18) =185806904840a(19) =406753277760a(20) =865727550900