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 A210981 #19 Jun 29 2023 20:55:38
%S A210981 0,1,7,11,23,30,48,58,82,95,125,141,177,196,238,260,308,333,387,415,
%T A210981 475,506,572,606,678,715,793,833,917,960,1050,1096,1192,1241,1343,
%U A210981 1395,1503,1558,1672,1730,1850,1911,2037,2101,2233,2300,2438,2508,2652,2725,2875,2951,3107,3186,3348
%N A210981 A062725 and positive terms of A051682 interleaved.
%C A210981 Vertex number of a square spiral similar to A195160.
%H A210981 <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,-2,-1,1).
%F A210981 G.f.: -x*(1+6*x+2*x^2) / ( (1+x)^2*(x-1)^3 ). - _R. J. Mathar_, Aug 07 2012
%F A210981 a(n) = ( 18*n^2+14*n-5+(6*n+5)*(-1)^n )/16. - _Luce ETIENNE_, Oct 14 2014
%t A210981 LinearRecurrence[{1,2,-2,-1,1},{0,1,7,11,23},70] (* _Harvey P. Dale_, Jun 29 2023 *)
%Y A210981 Members of this family are A093005, A210977, A006578, A210978, A181995, this sequence, A210982.
%Y A210981 Cf. A051682, A062725, A195160.
%K A210981 nonn,easy
%O A210981 0,3
%A A210981 _Omar E. Pol_, Aug 03 2012