A044973 Numbers whose base-3 representation contains exactly one 0 and three 1's.
31, 37, 39, 95, 97, 103, 113, 115, 119, 123, 127, 129, 139, 145, 147, 175, 193, 199, 201, 287, 293, 295, 311, 313, 319, 341, 347, 349, 359, 371, 375, 383, 385, 389, 393, 397, 399, 419, 421, 427, 437, 439, 443, 447, 451, 453, 463
Offset: 1
Examples
31 = 1011_3; 37 = 1101_3; 39 = 1110_3; 95 = 10112_3.
Links
- Robert Israel, Table of n, a(n) for n = 1..10000
Crossrefs
Programs
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Maple
f:= proc(d) local x,R,i,j,j3; x:= 3^d-1; op(sort([seq(seq(x - add(3^j, j = j3) - 2*3^i, i= {$0..d-2} minus j3) , j3 =combinat:-choose({$0..d-1},3))])) end proc: map(f, [$4..6]); # Robert Israel, Apr 20 2021 -
Mathematica
Select[Range[500],DigitCount[#,3,0]==1&&DigitCount[#,3,1]==3&] (* Harvey P. Dale, Jul 12 2019 *)
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PARI
isok(k) = my(d=digits(k,3)); (#select(x->(x==0), d) == 1) && (#select(x->(x==1), d) == 3); \\ Michel Marcus, Apr 21 2021