A100281 - OEIS

%I #17 Jan 19 2023 11:03:18

%S 0,1,2,3,5,4,7,6,10,11,8,9,15,14,13,12,21,20,23,22,16,17,18,19,31,30,

%T 29,28,26,27,24,25,42,43,40,41,47,46,45,44,32,33,34,35,37,36,39,38,63,

%U 62,61,60,58,59,56,57,53,52,55,54,48,49,50,51,84,85,86,87,81,80,83,82,94

%N a(n) = A099896(A099896(n)).

%C Permutation of the natural numbers with inverse A100282;

%C A064707(n) = a(n) for n<64.

%H Ivan Neretin, <a href="/A100281/b100281.txt">Table of n, a(n) for n = 0..8191</a>

%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>

%F a(n) = n XOR floor(n/4) XOR floor(n/16). - _Ivan Neretin_, Sep 06 2017

%o (Python)

%o def A100281(n): return n^(m:=n>>2)^(m>>2) # _Chai Wah Wu_, Jan 19 2023

%Y Cf. A099896, A064707, A100282.

%K nonn,look

%O 0,3

%A _Reinhard Zumkeller_, Nov 11 2004