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Numbers with exactly 3 1's in base 5 expansion.
2

%I #11 Apr 02 2014 04:39:49

%S 31,131,151,155,157,158,159,161,166,171,181,206,231,281,406,531,631,

%T 651,655,657,658,659,661,666,671,681,706,731,751,755,757,758,759,761,

%U 766,771,775,777,778,779,785,787,788,789,790

%N Numbers with exactly 3 1's in base 5 expansion.

%H Vincenzo Librandi, <a href="/A023728/b023728.txt">Table of n, a(n) for n = 1..1000</a>

%t Select[ Range[ 800 ], (Count[ IntegerDigits[ #, 5 ], 1 ]==3)& ]

%K nonn,base,easy

%O 1,1

%A _Olivier GĂ©rard_