This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A185346 #28 Nov 08 2023 06:35:40
%S A185346 -8,-7,-5,-1,7,23,55,119,247,503,1015,2039,4087,8183,16375,32759,
%T A185346 65527,131063,262135,524279,1048567,2097143,4194295,8388599,16777207,
%U A185346 33554423,67108855,134217719,268435447,536870903,1073741815,2147483639,4294967287,8589934583
%N A185346 a(n) = 2^n - 9.
%H A185346 G. C. Greubel, <a href="/A185346/b185346.txt">Table of n, a(n) for n = 0..1000</a>
%H A185346 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2).
%F A185346 G.f.: ( -8+17*x ) / ( (2*x-1)*(x-1) ). - _R. J. Mathar_, Dec 17 2012
%F A185346 E.g.f.: exp(2*x) - 9*exp(x). - _G. C. Greubel_, Jun 28 2017
%F A185346 From _Elmo R. Oliveira_, Nov 08 2023: (Start)
%F A185346 a(n) = 2*a(n-1) + 9 with a(0) = -8.
%F A185346 a(n) = 3*a(n-1) - 2*a(n-2) for n > 1. (End)
%p A185346 A185346:=n->2^n-9: seq(A185346(n), n=0..50); # _Wesley Ivan Hurt_, Jun 28 2017
%t A185346 Table[2^n - 9, {n, 0, 40}] (* _T. D. Noe_, Dec 04 2012 *)
%o A185346 (PARI) a(n)=2^n-9 \\ _Charles R Greathouse IV_, Oct 07 2015
%Y A185346 Cf. A000225, A036563, A172252 (essentially the same).
%K A185346 sign,easy
%O A185346 0,1
%A A185346 _Andreas Rieber_, Dec 04 2012