a(n) = floor( Gamma(n + 1/6)/Gamma(1/6) ).

Terms

a(0) =1a(1) =0a(2) =0a(3) =0a(4) =1a(5) =5a(6) =28a(7) =177a(8) =1269a(9) =10365a(10) =95019a(11) =966032a(12) =10787362a(13) =131246245a(14) =1728075562a(15) =24481070469a(16) =371296235455