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 A080939 #6 Mar 30 2012 16:49:42 %S A080939 3,8,6,11,16,14,19,17,22,27,25,30,35,33,38,36,34,39,37,42,47,45,50,55, %T A080939 53,58,56,61,66,64,69,74,72,70,68,66,64,62,60,65,70,68,73,78,76,81,79, %U A080939 84,89,87,92,97,95,100,98,96,101,99,104,102,100,98,103,101,99 %N A080939 a(1)=3; for n>1, a(n)=a(n-1)-2 if n is already in the sequence, a(n)=a(n-1)+5 otherwise. %H A080939 B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="http://www.cs.uwaterloo.ca/journals/JIS/index.html">Numerical analogues of Aronson's sequence</a>, J. Integer Seqs., Vol. 6 (2003), #03.2.2. %H A080939 B. Cloitre, N. J. A. Sloane and M. J. Vandermast, <a href="http://arXiv.org/abs/math.NT/0305308">Numerical analogues of Aronson's sequence</a> (math.NT/0305308) %F A080939 a(n)-n (n >= 1) is periodic with period 168. %Y A080939 Cf. A080578, A080900, A080901. %K A080939 nonn,easy %O A080939 1,1 %A A080939 _N. J. A. Sloane_ and Benoit Cloitre, Apr 04 2003