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 A095720 #2 Mar 30 2012 17:37:53 %S A095720 1,3,2,5,4,8,6,12,7,15,9,18,10,20,11,23,13,27,14,29,16,32,17,35,19,39, %T A095720 21,42,22,44,24,48,25,51,26,53,28,56,30,60,31,63,33,66,34,68,36,72,37, %U A095720 75,38,77,40,80,41,83,43,87,45,90,46,92,47,95,49,99,50,101,52,104,54 %N A095720 a(1)=1 and, for n>1, a(n)=a(n-1)+Floor(3n/4) if n is even, else a(n)=smallest positive integer which has not yet appeared in the sequence. %C A095720 Conjecture. For even n, the ratio a(n)/a(n-1) is asymptotic to 2 as n becomes large. (At n=3000, the ratio is 2.0004446.) %Y A095720 Cf. A094077. %K A095720 nonn %O A095720 1,2 %A A095720 _John W. Layman_, Jul 08 2004