a(n) = 7*5^n.

Terms

a(0) =7a(1) =35a(2) =175a(3) =875a(4) =4375a(5) =21875a(6) =109375a(7) =546875a(8) =2734375a(9) =13671875a(10) =68359375a(11) =341796875a(12) =1708984375a(13) =8544921875a(14) =42724609375a(15) =213623046875