a(n) = 6*a(n-1) - 7*a(n-2) for n > 1; a(0) = 1, a(1) = 7.

Terms

a(0) =1a(1) =7a(2) =35a(3) =161a(4) =721a(5) =3199a(6) =14147a(7) =62489a(8) =275905a(9) =1218007a(10) =5376707a(11) =23734193a(12) =104768209a(13) =462469903a(14) =2041441955a(15) =9011362409a(16) =39778080769a(17) =175588947751a(18) =775087121123