cp's OEIS Frontend

A263018 If n is the i-th positive integer with binary weight j, then a(n) is the j-th positive integer with binary weight i.

%I A263018 #9 Oct 27 2015 21:22:34
%S A263018 1,3,2,7,5,11,4,15,23,47,6,95,13,27,8,31,191,383,55,767,111,223,9,
%T A263018 1535,447,895,14,1791,29,59,16,63,3071,6143,3583,12287,7167,14335,119,
%U A263018 24575,28671,57343,239,114687,479,959,10,49151,229375,458751,1919,917503
%N A263018 If n is the i-th positive integer with binary weight j, then a(n) is the j-th positive integer with binary weight i.
%C A263018 Binary weight is given by A000120.
%C A263018 This is a self-inverse permutation of the natural numbers.
%C A263018 The positive terms in the sequence A036563 give the fixed points.
%C A263018 A000120(n) = A263017(a(n)) for any n>0.
%C A263018 A263017(n) = A000120(a(n)) for any n>0.
%C A263018 a(2^(n+1)-1) = 2^n for any n>0.
%C A263018 a(2^n) = 2^(n+1)-1 for any n>0.
%H A263018 Paul Tek, <a href="/A263018/b263018.txt">Table of n, a(n) for n = 1..10000</a>
%H A263018 Paul Tek, <a href="/A263018/a263018.pl.txt">PERL program for this sequence</a>
%o A263018 (PARI) a(n) = {j = hammingweight(n); v = vector(n, k, hammingweight(k)); i = #select(x->x==j, v); nb = 0; k = 0; while(nb != j, k++; if (hammingweight(k) == i, nb++)); k;} \\ _Michel Marcus_, Oct 16 2015
%Y A263018 Cf. A000120, A036563, A263017.
%K A263018 nonn,base
%O A263018 1,2
%A A263018 _Paul Tek_, Oct 07 2015