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 A010020 #28 Jul 08 2025 01:27:53
%S A010020 1,33,126,281,498,777,1118,1521,1986,2513,3102,3753,4466,5241,6078,
%T A010020 6977,7938,8961,10046,11193,12402,13673,15006,16401,17858,19377,20958,
%U A010020 22601,24306,26073,27902,29793,31746,33761,35838,37977,40178,42441,44766,47153,49602
%N A010020 a(0) = 1, a(n) = 31*n^2 + 2 for n>0.
%H A010020 Bruno Berselli, <a href="/A010020/b010020.txt">Table of n, a(n) for n = 0..1000</a>
%H A010020 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (3,-3,1).
%F A010020 G.f.: (1+x)*(1+29*x+x^2)/(1-x)^3. - _Bruno Berselli_, Feb 07 2012
%F A010020 E.g.f.: (x*(x+1)*31+2)*e^x-1. - _Gopinath A. R._, Feb 14 2012
%F A010020 Sum_{n>=0} 1/a(n) = 3/4 + sqrt(62)/124 *Pi*coth(Pi*sqrt(62)/31) = 1.05093832062... - _R. J. Mathar_, May 07 2024
%t A010020 Join[{1}, 31 Range[40]^2 + 2] (* _Bruno Berselli_, Feb 07 2012 *)
%t A010020 Join[{1}, LinearRecurrence[{3, -3, 1}, {33, 126, 281}, 50]] (* _Vincenzo Librandi_, Aug 03 2015 *)
%o A010020 (Magma) [1] cat [31*n^2+2: n in [1..50]]; // _Vincenzo Librandi_, Aug 03 2015
%Y A010020 Cf. A206399.
%K A010020 nonn,easy
%O A010020 0,2
%A A010020 _N. J. A. Sloane_