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

Terms

a(0) =1a(1) =0a(2) =6a(3) =6a(4) =42a(5) =78a(6) =330a(7) =798a(8) =2778a(9) =7566a(10) =24234a(11) =69630a(12) =215034a(13) =632814a(14) =1923018a(15) =5719902a(16) =17258010a(17) =51577422a(18) =155125482a(19) =464590014a(20) =1395342906a(21) =4182882990a(22) =12554940426a(23) =37652238366a(24) =112981880922a(25) =338895311118