a(n) = 5^n + n.

Terms

a(0) =1a(1) =6a(2) =27a(3) =128a(4) =629a(5) =3130a(6) =15631a(7) =78132a(8) =390633a(9) =1953134a(10) =9765635a(11) =48828136a(12) =244140637a(13) =1220703138a(14) =6103515639a(15) =30517578140a(16) =152587890641a(17) =762939453142