cp's OEIS Frontend

A140265 Permutation of natural numbers: a(n) = A140263(n-1)+1.

%I A140265 #14 Jul 06 2025 12:39:58
%S A140265 1,2,3,6,8,4,7,5,9,18,23,16,22,17,24,12,20,10,19,11,21,15,26,13,25,14,
%T A140265 27,54,68,52,67,53,69,48,65,46,64,47,66,51,71,49,70,50,72,36,59,34,58,
%U A140265 35,60,30,56,28,55,29,57,33,62,31,61,32,63,45,77,43,76,44,78,39,74,37
%N A140265 Permutation of natural numbers: a(n) = A140263(n-1)+1.
%H A140265 Indranil Ghosh, <a href="/A140265/b140265.txt">Table of n, a(n) for n = 1..6561</a>
%H A140265 <a href="/index/Per#IntegerPermutation">Index entries for sequences that are permutations of the natural numbers</a>
%o A140265 (Scheme) (define (A140265 n) (+ 1 (A140263 (- n 1))))
%o A140265 (Python)
%o A140265 from sympy import ceiling
%o A140265 from sympy.ntheory.factor_ import digits
%o A140265 def a004488(n): return int("".join([str((3 - i)%3) for i in digits(n, 3)[1:]]), 3)
%o A140265 def a117968(n):
%o A140265     if n==1: return 2
%o A140265     if n%3==0: return 3*a117968(n/3)
%o A140265     elif n%3==1: return 3*a117968((n - 1)/3) + 2
%o A140265     else: return 3*a117968((n + 1)/3) + 1
%o A140265 def a117967(n): return 0 if n==0 else a117968(-n) if n<0 else a004488(a117968(n))
%o A140265 def a001057(n): return -(-1)**n*ceiling(n/2)
%o A140265 def a(n): return a117967(a001057(n - 1)) + 1 # _Indranil Ghosh_, Jun 07 2017
%Y A140265 Inverse: A140266.
%K A140265 nonn,look
%O A140265 1,2
%A A140265 _Antti Karttunen_, May 19 2008