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Numbers whose base-4 representation contains exactly one 1 and two 3's.
0

%I #14 May 21 2023 12:27:29

%S 31,55,61,79,111,115,123,124,126,159,183,189,199,205,211,219,220,222,

%T 231,237,241,244,246,249,271,303,307,315,316,318,399,431,435,443,444,

%U 446,451,459,460,462,483,491,492,494,496,498

%N Numbers whose base-4 representation contains exactly one 1 and two 3's.

%t b413Q[n_]:=Module[{dc=DigitCount[n,4]},dc[[1]]==1&&dc[[3]]==2]; Select[ Range[500],b413Q] (* _Harvey P. Dale_, Oct 22 2011 *)

%Y Cf. A007090.

%K nonn,base

%O 1,1

%A _Clark Kimberling_