Expansion of x^k/Product_{t=k..2k} (1-tx) for k=4.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =1a(5) =30a(6) =545a(7) =7770a(8) =95781a(9) =1071630a(10) =11192665a(11) =111095490a(12) =1060634861a(13) =9822843030a(14) =88799732385a(15) =787259974410