a(n) = 10*a(n-1) - 20*a(n-2), a(0)=1, a(1)=6.

Terms

a(0) =1a(1) =6a(2) =40a(3) =280a(4) =2000a(5) =14400a(6) =104000a(7) =752000a(8) =5440000a(9) =39360000a(10) =284800000a(11) =2060800000a(12) =14912000000a(13) =107904000000a(14) =780800000000