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 A141126 #18 Jul 18 2025 08:30:22
%S A141126 1,1,2,6,15,31,56,20,69,5,86,186,65,209,40,236,11,267,556,232,593,193,
%T A141126 634,150,679,103,728,52,781,1565,724,1624,663,1687,598,1754,529,1825,
%U A141126 456,1900,379,1979,298,2062,213,2149,124,2240,4449,2145,4546,2046,4647
%N A141126 a(n+1) = a(n)-n^2 if positive and new, else a(n+1) = a(n)+n^2; a(0)=1.
%H A141126 Indranil Ghosh, <a href="/A141126/b141126.txt">Table of n, a(n) for n = 0..50000</a> (terms 0..240 from Reinhard Zumkeller)
%H A141126 <a href="/index/Rea#Recaman">Index entries for sequences related to Recamán's sequence</a>.
%t A141126 s={1};Do[nx=s[[-1]]-n^2;If[nx>0&&!MemberQ[s,nx],AppendTo[s,nx],AppendTo[s,nx+2n^2]],{n,0,51}];s (* _James C. McMahon_, Jul 17 2025 *)
%Y A141126 Cf. A063733.
%K A141126 nonn
%O A141126 0,3
%A A141126 _Reinhard Zumkeller_, Jun 05 2008