a(n) = n*5^n + 1.

Terms

a(0) =1a(1) =6a(2) =51a(3) =376a(4) =2501a(5) =15626a(6) =93751a(7) =546876a(8) =3125001a(9) =17578126a(10) =97656251a(11) =537109376a(12) =2929687501a(13) =15869140626a(14) =85449218751a(15) =457763671876