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 A081746 #15 Aug 13 2019 23:03:21 %S A081746 1,6,11,16,21,18,23,28,33,38,35,40,45,50,55,52,57,54,59,64,61,66,63, %T A081746 68,73,78,83,80,85,90,95,100,97,102,99,104,109,106,111,108,113,118, %U A081746 123,128,125,130,135,140,145,142,147,144,149,146,143,148,145,150 %N A081746 a(1)=1; for n>1, a(n)=a(n-1)-3 if n is already in the sequence, a(n)=a(n-1)+5 otherwise. %H A081746 Peter Munn, <a href="/A081746/b081746.txt">Table of n, a(n) for n = 1..5000</a> %H A081746 B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="https://cs.uwaterloo.ca/journals/JIS/VOL6/Cloitre/cloitre2.html">Numerical analogues of Aronson's sequence</a>, J. Integer Seqs., Vol. 6 (2003), #03.2.2. %H A081746 B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="https://arxiv.org/abs/math/0305308">Numerical analogues of Aronson's sequence</a>, arXiv:math/0305308 [math.NT], 2003. %F A081746 a(n) - n is periodic with period 648. %t A081746 a[n_] := a[n] = If[n == 1, 1, If[MemberQ[Array[a, n-1], n], a[n-1] - 3, a[n-1] + 5]]; Array[a, 58] (* _Jean-François Alcover_, Oct 05 2018 *) %Y A081746 Cf. A081747, A081748, A080578, A080900, A080901, A080939. %K A081746 nonn,look,hear %O A081746 1,2 %A A081746 _Benoit Cloitre_, Apr 05 2003