a(n) = 5*a(n-1) - a(n-2), with a(1)=1, a(2)=4.

Terms

a(0) =1a(1) =4a(2) =19a(3) =91a(4) =436a(5) =2089a(6) =10009a(7) =47956a(8) =229771a(9) =1100899a(10) =5274724a(11) =25272721a(12) =121088881a(13) =580171684a(14) =2779769539a(15) =13318676011a(16) =63813610516a(17) =305749376569