a(n) = 11*5^n+1.

Terms

a(0) =12a(1) =56a(2) =276a(3) =1376a(4) =6876a(5) =34376a(6) =171876a(7) =859376a(8) =4296876a(9) =21484376a(10) =107421876a(11) =537109376a(12) =2685546876a(13) =13427734376a(14) =67138671876a(15) =335693359376