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 A156568 #11 Apr 18 2024 09:20:53
%S A156568 23,115,667,3887,22655,132043,769603,4485575,26143847,152377507,
%T A156568 888121195,5176349663,30169976783,175843511035,1024891089427,
%U A156568 5973503025527,34816127063735,202923259356883,1182723429077563
%N A156568 a(n) = 6*a(n-1)-a(n-2) for n > 2; a(1)=23, a(2)=115.
%H A156568 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (6,-1).
%F A156568 a(n) = 23*((2+sqrt(2))*(3-2*sqrt(2))^n +(2-sqrt(2))*(3+2*sqrt(2))^n)/4.
%F A156568 G.f.: 23*x*(1-x)/(1-6*x+x^2). [corrected by _Klaus Brockhaus_, Sep 22 2009]
%F A156568 Limit_{n -> oo} a(n)/a(n-1) = 3+2*sqrt(2).
%o A156568 (PARI) {m=19; v=concat([23, 115], vector(m-2)); for(n=3, m, v[n]=6*v[n-1]-v[n-2]); v}
%Y A156568 Second trisection of A156567. Equals 23*A001653.
%Y A156568 Cf. A156035 (decimal expansion of 3+2*sqrt(2)), A156569, A156570.
%K A156568 nonn,easy
%O A156568 1,1
%A A156568 _Klaus Brockhaus_, Feb 11 2009, Feb 16 2009