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 A213543 #19 May 22 2021 04:30:40 %S A213543 0,1,0,3,0,1,0,3,0,1,8,11,0,1,8,11,0,1,0,19,16,17,16,3,0,1,8,27,16,17, %T A213543 24,11,0,1,0,3,0,33,0,3,32,33,40,43,32,1,40,43,0,1,0,19,16,49,16,3,32, %U A213543 33,40,59,48,17,56,43,0,1,0,3,64,65,64,3,0,65,8,75 %N A213543 a(n) = n AND 3^n, where AND is the bitwise AND operator. %C A213543 Indices of 0's: %C A213543 0, 2, 4, 6, 8, 12, 16, 18, 24, 32, 34, 36, 38, 48, 50, 64, 66, 72, 96, 98, 128, 130, 132, 144, 146, 166, 192, 194, 256, 258, 260, 262, 280, 288, 290, 292, 328, 384, 386, 388, 512, 514, ... %C A213543 Indices of 1's: %C A213543 1, 5, 9, 13, 17, 25, 33, 45, 49, 65, 89, 97, 129, 173, 177, 193, 257, 261, 265, 281, 353, 385, 513, 517, 521, 529, 561, 601, 685, 705, 769, 773, 777, 1025, 1029, 1037, 1049, 1057, 1073, ... %C A213543 n's such that a(n)=n: %C A213543 0, 1, 3, 11, 19, 27, 43, 59, 75, 83, 107, 139, 147, 155, 203, 211, 267, 275, 283, 299, 315, 395, 403, 411, 523, 531, 539, 555, 571, 587, 595, 619, 779, 787, 795, 811, 827, 1051, 1083, ... %H A213543 Alois P. Heinz, <a href="/A213543/b213543.txt">Table of n, a(n) for n = 0..8192</a> %p A213543 a:= proc(n) local i, k, m, r; %p A213543 k:= n; %p A213543 m:= 3 &^ k mod (2^(1+ilog2(1+k))); %p A213543 r:= 0; %p A213543 for i from 0 while (m>0 or k>0) do %p A213543 r:= r +2^i* irem(m, 2, 'm') *irem(k, 2, 'k') %p A213543 od; r %p A213543 end: %p A213543 seq(a(n), n=0..100); # _Alois P. Heinz_, Jun 22 2012 %o A213543 (Python) %o A213543 print([3**n & n for n in range(99)]) %Y A213543 Cf. A213526, A213542. %K A213543 nonn,base,easy,look,less %O A213543 0,4 %A A213543 _Alex Ratushnyak_, Jun 14 2012