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A140263 Permutation of nonnegative integers obtained by interleaving A117967 and A117968.

%I A140263 #21 Jul 09 2025 04:29:22
%S A140263 0,1,2,5,7,3,6,4,8,17,22,15,21,16,23,11,19,9,18,10,20,14,25,12,24,13,
%T A140263 26,53,67,51,66,52,68,47,64,45,63,46,65,50,70,48,69,49,71,35,58,33,57,
%U A140263 34,59,29,55,27,54,28,56,32,61,30,60,31,62,44,76,42,75,43,77,38,73,36
%N A140263 Permutation of nonnegative integers obtained by interleaving A117967 and A117968.
%H A140263 A. Karttunen, <a href="/A140263/b140263.txt">Table of n, a(n) for n = 0..2186</a>
%H A140263 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%F A140263 a(n) = A117967(A001057(n)). (Assuming that the domain of A117967 is the whole Z line.)
%o A140263 (Python)
%o A140263 from sympy import ceiling
%o A140263 from sympy.ntheory.factor_ import digits
%o A140263 def a004488(n): return int("".join([str((3 - i)%3) for i in digits(n, 3)[1:]]), 3)
%o A140263 def a117968(n):
%o A140263     if n==1: return 2
%o A140263     if n%3==0: return 3*a117968(n/3)
%o A140263     elif n%3==1: return 3*a117968((n - 1)/3) + 2
%o A140263     else: return 3*a117968((n + 1)/3) + 1
%o A140263 def a117967(n): return 0 if n==0 else a117968(-n) if n<0 else a004488(a117968(n))
%o A140263 def a001057(n): return -(-1)**n*ceiling(n/2)
%o A140263 def a(n): return a117967(a001057(n)) # _Indranil Ghosh_, Jun 07 2017
%Y A140263 Inverse: A140264. Bisections: A117967 & A117968. a(n) = A140265(n+1)-1.
%Y A140263 Cf. A004488, A117966.
%K A140263 nonn,look,hear
%O A140263 0,3
%A A140263 _Antti Karttunen_, May 19 2008, originally described in a posting at the SeqFan mailing list on Sep 15 2005