First differences of 8^n (A001018).

Terms

a(0) =1a(1) =7a(2) =56a(3) =448a(4) =3584a(5) =28672a(6) =229376a(7) =1835008a(8) =14680064a(9) =117440512a(10) =939524096a(11) =7516192768a(12) =60129542144a(13) =481036337152