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 A138466 #14 Jan 20 2024 16:14:49 %S A138466 1,2,2,3,4,5,5,6,7,8,8,9,10,10,11,12,13,13,14,15,16,16,17,18,19,19,20, %T A138466 21,21,22,23,24,24,25,26,27,27,28,29,30,30,31,32,32,33,34,35,35,36,37, %U A138466 38,38,39,40,40,41,42,43,43,44,45,46,46,47,48,49,49,50,51,51,52,53,54 %N A138466 a(1)=1; for n >= 2, a(n) = n - floor((1/2)*a(a(n-1))). %H A138466 Michel Dekking, <a href="/A138466/a138466.png">Proof by Benoit Cloitre</a> %F A138466 For n >= 1, a(n) = floor((sqrt(3)-1)*(n+1)). %t A138466 Floor[(Sqrt[3] - 1)*(Range[100] + 1)] (* _Wesley Ivan Hurt_, Jan 20 2024 *) %o A138466 (PARI) a(n)=floor((sqrt(3)-1)*(n+1)) %Y A138466 Cf. A005206, A138467, A160390. %K A138466 nonn,easy %O A138466 1,2 %A A138466 _Benoit Cloitre_, May 09 2008