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 A140323 #28 Sep 29 2024 16:02:16 %S A140323 1,9,31,129,511,2049,8191,32769,131071,524289,2097151,8388609, %T A140323 33554431,134217729,536870911,2147483649,8589934591,34359738369, %U A140323 137438953471,549755813889,2199023255551,8796093022209,35184372088831,140737488355329,562949953421311 %N A140323 First differences of A140322. %H A140323 Vincenzo Librandi, <a href="/A140323/b140323.txt">Table of n, a(n) for n = 1..1000</a> %H A140323 <a href="/index/Rec#order_02">Index entries for linear recurrences with constant coefficients</a>, signature (3,4). %F A140323 Mix A004171(2*n)-1, A004171(2*n+1)+1. %F A140323 a(n+1)-4*a(n) = period 2: repeat [5, -5]. %F A140323 G.f.: x*(1 + 6*x)/(1 - 3*x - 4*x^2). - _Ilya Gutkovskiy_, May 11 2016 %F A140323 From _Klaus Purath_, Aug 03 2020: (Start) %F A140323 a(n) = 8*A015521(n-1) + A102900(n-1). %F A140323 a(n) = 30*4^(n-3) + a(n-2), n>2. %F A140323 a(n+2) = 3*a(n+1) + 4*a(n). (End) %t A140323 a[n_] := (2*4^n - (-1)^n); Array[a, 25, 0] (* _Robert G. Wilson v_, Aug 13 2011 *) %Y A140323 Cf. A140322. %K A140323 nonn,easy %O A140323 1,2 %A A140323 _Paul Curtz_, May 26 2008 %E A140323 Extended and offset changed from 0 to 1 by _Vincenzo Librandi_, Aug 09 2011