a(n) = n + n*(n-1)*(n-2)*(n-3)*(n-4).

Terms

a(0) =0a(1) =1a(2) =2a(3) =3a(4) =4a(5) =125a(6) =726a(7) =2527a(8) =6728a(9) =15129a(10) =30250a(11) =55451a(12) =95052a(13) =154453a(14) =240254a(15) =360375a(16) =524176a(17) =742577a(18) =1028178a(19) =1395379a(20) =1860500a(21) =2441901a(22) =3160102a(23) =4037903a(24) =5100504a(25) =6375625a(26) =7893626a(27) =9687627a(28) =11793628a(29) =14250629