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%I #6 Mar 30 2012 18:50:53
%S 1,2,3,7,6,5,4,11,10,9,8,15,14,13,12,31,30,29,28,27,26,25,24,23,22,21,
%T 20,19,18,17,16,47,46,45,44,43,42,41,40,39,38,37,36,35,34,33,32,63,62,
%U 61,60,59,58,57,56,55,54,53,52,51,50,49,48,127,126,125,124,123,122,121
%N a(n) = if n<4 then n else 4*a(floor(n/4)) + 3 - n mod 4.
%C Self-inverse permutation of the natural numbers;
%C A115310(n+2,3) = a(n);
%C if n is written in base 4 representation, then a(n) is the value after replacing all digits d (but not the leading one) by 3-d.
%H <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%Y Cf. A054429, A115303, A115305, A115306, A115307, A115308, A115309, A106649.
%K nonn,base
%O 1,2
%A _Reinhard Zumkeller_, Jan 20 2006
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