a(n) = floor( Gamma(n + 4/5)/Gamma(4/5) ).

Terms

a(0) =1a(1) =0a(2) =1a(3) =4a(4) =15a(5) =73a(6) =426a(7) =2900a(8) =22624a(9) =199094a(10) =1951127a(11) =21072175a(12) =248651668a(13) =3182741351a(14) =43921830647a(15) =650043093588