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 A010015 #37 May 07 2024 06:03:56
%S A010015 1,27,102,227,402,627,902,1227,1602,2027,2502,3027,3602,4227,4902,
%T A010015 5627,6402,7227,8102,9027,10002,11027,12102,13227,14402,15627,16902,
%U A010015 18227,19602,21027,22502,24027,25602,27227,28902,30627,32402,34227,36102,38027,40002
%N A010015 a(0) = 1, a(n) = 25*n^2 + 2 for n > 0.
%C A010015 Subsequence of A160842. - _Bruno Berselli_, Feb 06 2012
%C A010015 The identity (25*n^2 + 1)^2 - (25*n^2 + 2)*(5*n)^2 = 1 can be written as (A016850(n+1) + 1)^2 - a(n+1)*A008587(n+1)^2 = 1. - _Vincenzo Librandi_, Feb 08 2012
%H A010015 Bruno Berselli, <a href="/A010015/b010015.txt">Table of n, a(n) for n = 0..1000</a>
%H A010015 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A010015 G.f.: (1+x)*(1 + 23*x + x^2)/(1-x)^3. - _Bruno Berselli_, Feb 06 2012
%F A010015 E.g.f.: (x*(x+1)*25 + 2)*e^x - 1. - _Gopinath A. R._, Feb 14 2012
%F A010015 Sum_{n>=0} 1/a(n) =3/4+sqrt(2)/20*Pi*coth(Pi*sqrt(2)/5) = 1.062575323280590.. - _R. J. Mathar_, May 07 2024
%F A010015 a(n) = A262221(n)+A262221(n+1). - _R. J. Mathar_, May 07 2024
%t A010015 Join[{1}, 25 Range[40]^2 + 2] (* _Bruno Berselli_, Feb 06 2012 *)
%t A010015 Join[{1}, LinearRecurrence[{3, -3, 1}, {27, 102, 227}, 50]] (* _Vincenzo Librandi_, Feb 08 2012 *)
%o A010015 (PARI) A010015(n)=25*n^2+2-!n \\ _M. F. Hasler_, Feb 14 2012
%Y A010015 Cf. A206399.
%K A010015 nonn,easy
%O A010015 0,2
%A A010015 _N. J. A. Sloane_