A007959 - OEIS

%I #17 Nov 21 2016 04:18:39

%S 10,11,12,13,14,15,16,17,18,19,30,31,32,33,34,35,36,37,38,39,50,51,52,

%T 53,54,55,56,57,58,59,70,71,72,73,74,75,76,77,78,79,90,91,92,93,94,95,

%U 96,97,98,99,100,101,102,103

%N Some nontrivial permutation of digits is an odd number.

%C Also: Odd numbers with more than 2 digits (so you can swap any two digits other than the last one), or numbers having at least one odd digit not in the last position (so you can swap that one with the last digit). - _M. F. Hasler_, Sep 30 2012

%H Robert Israel, <a href="/A007959/b007959.txt">Table of n, a(n) for n = 1..10000</a>

%H F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/OPNS.pdf">Only Problems, Not Solutions!</a>

%F a(n) ~ n. - _Charles R Greathouse IV_, Sep 19 2012

%e The transposition (1,2) (nontrivial permutation of order two) acting on 11 yields the odd number 11. - _M. F. Hasler_, Sep 30 2012

%p filter:= proc(n) local L;

%p   L:= convert(n,base,10) mod 2;

%p   (L[1]=1 and nops(L) > 2) or max(L[2..-1])=1

%p end proc:

%p select(filter, [$10..1000]); # _Robert Israel_, Nov 21 2016

%o (PARI) is_A007959(n)=bittest(n,0)&n>99 || while(n\=10, bittest(n,0) & return(1)) \\ _M. F. Hasler_, Sep 30 2012

%Y Cf. A007930.

%K nonn,base

%O 1,1

%A R. Muller