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 A086225 #32 May 05 2025 04:47:58
%S A086225 10,21,43,87,175,351,703,1407,2815,5631,11263,22527,45055,90111,
%T A086225 180223,360447,720895,1441791,2883583,5767167,11534335,23068671,
%U A086225 46137343,92274687,184549375,369098751,738197503,1476395007,2952790015
%N A086225 a(n) = 11*2^n - 1.
%C A086225 (a(n-1))^2 + a(n) is a square. - _Vincenzo Librandi_, Aug 08 2010
%H A086225 Harvey P. Dale, <a href="/A086225/b086225.txt">Table of n, a(n) for n = 0..1000</a>
%H A086225 Gennady Eremin, <a href="https://arxiv.org/abs/2405.16143">Partitioning the set of natural numbers into Mersenne trees and into arithmetic progressions; Natural Matrix and Linnik's constant</a>, arXiv:2405.16143 [math.CO], 2024. See pp. 3-4.
%H A086225 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,-2).
%F A086225 a(n) = 2*a(n-1) + 1.
%F A086225 G.f.: (10 - 9*x)/((2*x - 1)*(x - 1)). - _R. J. Mathar_, Oct 22 2011
%F A086225 E.g.f.: exp(x)*(11*exp(x) - 1). - _Stefano Spezia_, May 05 2025
%t A086225 NestList[2#+1&,10,30] (* or *) LinearRecurrence[{3,-2},{10,21},30] (* _Harvey P. Dale_, Nov 25 2013 *)
%o A086225 (PARI) a(n) = 11*2^n - 1 \\ _Michel Marcus_, Jul 15 2013
%Y A086225 Cf. A000079, A005015.
%K A086225 nonn,easy
%O A086225 0,1
%A A086225 _Marco Matosic_, Jul 29 2003