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 A220088 #18 Nov 11 2023 10:59:53
%S A220088 -80,-79,-77,-73,-65,-49,-17,47,175,431,943,1967,4015,8111,16303,
%T A220088 32687,65455,130991,262063,524207,1048495,2097071,4194223,8388527,
%U A220088 16777135,33554351,67108783,134217647,268435375,536870831,1073741743,2147483567,4294967215
%N A220088 a(n) = 2^n - 81.
%H A220088 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2).
%F A220088 From _Chai Wah Wu_, Jan 17 2020: (Start)
%F A220088 a(n) = 3*a(n-1) - 2*a(n-2) for n > 1.
%F A220088 G.f.: (161*x - 80)/((x - 1)*(2*x - 1)). (End)
%F A220088 From _Elmo R. Oliveira_, Nov 11 2023: (Start)
%F A220088 a(n) = 2*a(n-1) + 81 with a(0) = -80.
%F A220088 E.g.f.: exp(2*x) - 81*exp(x). (End)
%t A220088 Table[2^n - 81, {n, 0, 40}] (* _T. D. Noe_, Dec 04 2012 *)
%Y A220088 Cf. A000225, A036563, A185346, A220087.
%K A220088 sign,easy
%O A220088 0,1
%A A220088 _Andreas Rieber_, Dec 04 2012