a(n) = 2*a(n-1) + 10*a(n-2), with a(0) = 1, a(1) = 2.

Terms

a(0) =1a(1) =2a(2) =14a(3) =48a(4) =236a(5) =952a(6) =4264a(7) =18048a(8) =78736a(9) =337952a(10) =1463264a(11) =6306048a(12) =27244736a(13) =117549952a(14) =507547264a(15) =2190594048a(16) =9456660736a(17) =40819261952a(18) =176205131264a(19) =760602882048