a(n) = Sum_{i=1..n} C(i+3,4)^3.

Terms

a(0) =1a(1) =126a(2) =3501a(3) =46376a(4) =389376a(5) =2389752a(6) =11650752a(7) =47587752a(8) =168875127a(9) =534401002a(10) =1537404003a(11) =4080706128a(12) =10109274128a(13) =23590546128a(14) =52243162128a(15) =110473767504a(16) =224205418629a(17) =438589465254a(18) =830009446129