A188341 Numbers having no 0's and not more than one 1 in their representation in base 3.

1, 2, 5, 7, 8, 17, 23, 25, 26, 53, 71, 77, 79, 80, 161, 215, 233, 239, 241, 242, 485, 647, 701, 719, 725, 727, 728, 1457, 1943, 2105, 2159, 2177, 2183, 2185, 2186, 4373, 5831, 6317, 6479, 6533, 6551, 6557, 6559, 6560, 13121, 17495, 18953

Offset: 1

Author

Vladimir Shevelev, Apr 02 2011

Keywords

• nonn
• base

Links

• Alois P. Heinz, Table of n, a(n) for n = 1..1000
• V. Shevelev, Binomial Coefficient Predictors, Journal of Integer Sequences, Vol. 14 (2011), Article 11.2.8

Crossrefs

Cf. A062756, A077267.

Programs

Maple

a:= proc(n) option remember; local i, l, m, t;
      m:= `if`(n=1, 0, a(n-1));
      l:= NULL;
      for t while m>0 do l:= l, irem(m, 3, 'm') od;
      l:= array([l, 0]);
      for i while l[i]=2 do od;
      if l[i]=0 then l[i]:= 1
                else l[i]:= 2;
                     if i>1 then l[i-1]:= 1 fi
      fi;
      add(l[i] *3^(i-1), i=1..t)
    end:
seq(a(n), n=1..100);  # Alois P. Heinz, Apr 02 2011

Mathematica

okQ[n_]:=DigitCount[n,3,0]==0&&DigitCount[n,3,1]<2; Select[Range[20000], okQ]  (* Harvey P. Dale, Apr 16 2011 *)