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 A269969 #15 May 21 2023 08:24:35
%S A269969 0,5,16,20,42,47,51,88,97,102,106,164,175,182,187,191,274,289,300,307,
%T A269969 312,316,428,447,460,469,476,481,485,632,657,672,685,694,701,706,710,
%U A269969 894,923,944,959,970,979,986,991,995,1222,1257,1282,1299,1314,1325,1334
%N A269969 Index of first occurrence of -n in A269783.
%C A269969 Sequence A269783 is defined by A269783(0)=0 and A269783(n+1) = A269783(n) + (-1)^(k+e)*floor(k/2), where k = #{ j<=n | A269783(j)=A269783(n) } and e=1 for A269783(n)>0, else e=0. That is, the 1st, 2nd, 3rd, 4th... occurrence of any positive integer n is followed by n resp. n-1 resp. n+1 resp. n-2, etc., and for zero or negative integers the same with opposite sign.
%H A269969 Rémy Sigrist, <a href="/A269969/b269969.txt">Table of n, a(n) for n = 0..10000</a>
%H A269969 Rémy Sigrist, <a href="/A269969/a269969.gp.txt">PARI program</a>
%o A269969 (PARI) See Links section.
%Y A269969 Cf. A269783 (main sequence), A269967 (indices of zeros), A269968 (index of first occurrence of n).
%K A269969 nonn
%O A269969 0,2
%A A269969 _M. F. Hasler_, Mar 08 2016
%E A269969 More terms from _Rémy Sigrist_, May 21 2023