a(n) = 5^n + 5.

Terms

a(0) =6a(1) =10a(2) =30a(3) =130a(4) =630a(5) =3130a(6) =15630a(7) =78130a(8) =390630a(9) =1953130a(10) =9765630a(11) =48828130a(12) =244140630a(13) =1220703130a(14) =6103515630a(15) =30517578130a(16) =152587890630a(17) =762939453130