A039089 - OEIS

%I #15 Jun 24 2021 23:57:18

%S 0,2,3,4,5,6,8,16,18,20,21,22,23,24,26,27,29,30,31,32,33,35,36,38,39,

%T 40,41,42,44,45,47,48,49,50,51,53,54,56,57,58,59,60,62,64,72,74,75,76,

%U 77,78,80,88,106,115,124,133,142,144,146,147,148,149,150,152,160,162

%N Numbers whose base-9 representation has the same number of 1's and 7's.

%H G. C. Greubel, <a href="/A039089/b039089.txt">Table of n, a(n) for n = 1..5000</a>

%t Select[Range[0, 500], DigitCount[#, 9, 1] == DigitCount[#, 9, 7] &] (* _G. C. Greubel_, Nov 01 2017 *)

%o (PARI) isok(n) = my(d=digits(n, 9)); #select(x->(x==1), d) == #select(x->(x==7), d); \\ _Michel Marcus_, Nov 01 2017

%K nonn,base,easy

%O 1,2

%A _Olivier Gérard_