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Inverse permutation of A139080 (a(n+1) = least unused m such that floor(max(m,a(n))/min(m,a(n))) = 2).
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%I #6 Apr 28 2015 16:41:55

%S 1,2,5,3,8,6,11,4,16,9,14,7,19,12,24,29,34,17,22,10,27,15,32,37,42,20,

%T 47,13,52,25,57,30,40,35,45,18,50,23,55,62,67,28,60,72,77,33,82,38,87,

%U 43,92,21,97,48,65,70,102,53,75,26,80,58,85,31,107,41,90,36,95,46,100

%N Inverse permutation of A139080 (a(n+1) = least unused m such that floor(max(m,a(n))/min(m,a(n))) = 2).

%C A139080 was only conjectured to be a permutation, until a proof has been proposed recently.

%H M. F. Hasler, <a href="/A257280/b257280.txt">Table of n, a(n) for n = 1..2500</a>

%H <a href="/index/Per#IntegerPermutation">OEIS Index entries of sequences related to permutations of the nonnegative integers.</a>

%o (PARI) A257280=vecsort(A=A139080,,1); for(i=1,#A, A[A257280[i]]==i||return(A257280=A257280[1..i-1]))

%K nonn

%O 1,2

%A _M. F. Hasler_, Apr 26 2015