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

Terms

a(0) =2a(1) =11a(2) =36a(3) =141a(4) =646a(5) =3151a(6) =15656a(7) =78161a(8) =390666a(9) =1953171a(10) =9765676a(11) =48828181a(12) =244140686a(13) =1220703191a(14) =6103515696a(15) =30517578201a(16) =152587890706a(17) =762939453211