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Numbers whose base-9 representation has the same number of 1's and 6's.
1

%I #16 Jun 25 2021 01:42:40

%S 0,2,3,4,5,7,8,15,18,20,21,22,23,25,26,27,29,30,31,32,34,35,36,38,39,

%T 40,41,43,44,45,47,48,49,50,52,53,55,63,65,66,67,68,70,71,72,74,75,76,

%U 77,79,80,87,105,114,123,132,135,137,138,139,140,142,143,150,159,162

%N Numbers whose base-9 representation has the same number of 1's and 6's.

%H Robert Israel, <a href="/A039088/b039088.txt">Table of n, a(n) for n = 1..10000</a>

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

%p L:= convert(n,base,9);

%p numboccur(1,L) = numboccur(6,L)

%p end proc:

%p select(filter, [$0..1000]); # _Robert Israel_, Mar 13 2018

%o (PARI) isok(n) = {my(d = digits(n, 9)); #select(x->(x==1), d) == #select(x->(x==6), d);} \\ _Michel Marcus_, Mar 13 2018

%Y Cf. A007095.

%K nonn,base,easy

%O 1,2

%A _Olivier GĂ©rard_