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 A158230 #25 Aug 19 2025 08:54:03
%S A158230 258,1028,2310,4104,6410,9228,12558,16400,20754,25620,30998,36888,
%T A158230 43290,50204,57630,65568,74018,82980,92454,102440,112938,123948,
%U A158230 135470,147504,160050,173108,186678,200760,215354,230460,246078,262208,278850,296004
%N A158230 a(n) = 256*n^2 + 2*n.
%C A158230 The identity (256*n+1)^2-(256*n^2+2*n)*(16)^2=1 can be written as A158231(n)^2-a(n)*(16)^2=1.
%H A158230 Vincenzo Librandi, <a href="/A158230/b158230.txt">Table of n, a(n) for n = 1..10000</a>
%H A158230 Vincenzo Librandi, <a href="http://mathforum.org/kb/message.jspa?messageID=5785989&tstart=0">X^2-AY^2=1</a>
%H A158230 E. J. Barbeau, <a href="http://www.math.toronto.edu/barbeau/home.html">Polynomial Excursions</a>, Chapter 10: <a href="http://www.math.toronto.edu/barbeau/hxpol10.pdf">Diophantine equations</a> (2010), pages 84-85 (row 15 in the first table at p. 85, case d(t) = t*(16^2*t+2)).
%H A158230 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A158230 a(n) = 3*a(n-1) -3*a(n-2) +a(n-3).
%F A158230 G.f.: 2*x*(129+127*x)/(1-x)^3.
%F A158230 E.g.f.: 2*exp(x)*x*(129 + 128*x). - _Stefano Spezia_, Aug 19 2025
%t A158230 LinearRecurrence[{3,-3,1},{258,1028,2310},50]
%o A158230 (Magma) I:=[258, 1028, 2310]; [n le 3 select I[n] else 3*Self(n-1)-3*Self(n-2)+1*Self(n-3): n in [1..50]];
%o A158230 (PARI) a(n) = 256*n^2+2*n
%Y A158230 Cf. A158231.
%K A158230 nonn,easy
%O A158230 1,1
%A A158230 _Vincenzo Librandi_, Mar 14 2009