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 A081260 #5 Mar 30 2012 17:27:18 %S A081260 4,10,16,21,26,32,38,44,50,55,60,66,72,78,84,89,94,100,106,112,117, %T A081260 122,128,134,140,145,150,156,162,168,174,179,184,190,196,202,208,213, %U A081260 218,224,230,236,242,247,252,258,264,270,276,281,286,292,298,304,309,314 %N A081260 a(1)=4; for n>1, a(n) is taken to be the third-smallest integer greater than a(n-1) such that the condition "n is a member of the sequence if and only if a(n) is odd" is satisfied. %H A081260 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 A081260 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) %e A081260 a(1)=4, implying that the fourth term is the first odd member of the sequence; hence a(2) and a(3) are even. The third-smallest even integer greater than 4 is 10; therefore a(2)=10. The third-smallest integers that can satisfy the given condition if taken as a(3) and a(4) are 16 and 21, respectively. %Y A081260 Cf. A079000, A080753. %K A081260 easy,nonn %O A081260 1,1 %A A081260 _Matthew Vandermast_, Mar 14 2003