a(n) = 10*a(n-1) - 20*a(n-2), a(0)=1,a(1)=5.

Terms

a(0) =1a(1) =5a(2) =30a(3) =200a(4) =1400a(5) =10000a(6) =72000a(7) =520000a(8) =3760000a(9) =27200000a(10) =196800000a(11) =1424000000a(12) =10304000000a(13) =74560000000a(14) =539520000000