A125292 Numbers having either no ones or no twos in their ternary representation.

1, 2, 3, 4, 6, 8, 9, 10, 12, 13, 18, 20, 24, 26, 27, 28, 30, 31, 36, 37, 39, 40, 54, 56, 60, 62, 72, 74, 78, 80, 81, 82, 84, 85, 90, 91, 93, 94, 108, 109, 111, 112, 117, 118, 120, 121, 162, 164, 168, 170, 180, 182, 186, 188, 216, 218, 222, 224, 234, 236, 240, 242, 243

Offset: 1

Author

Reinhard Zumkeller, Nov 26 2006

Keywords

• nonn
• base
• easy

Comments

Complement of A125293; union of A005823 and A005836;

A125291(a(n)) = 1; A062756(a(n))*A081603(a(n)) = 0.

Links

• Rémy Sigrist, Table of n, a(n) for n = 1..8190
• Eric Weisstein's World of Mathematics, Ternary
• Eric Weisstein's World of Mathematics, Repdigit

Crossrefs

Subsequence of A154314.

Cf. A007089, A125289.

Programs

Mathematica

not[n_]:=Module[{c=DigitCount[n,3]},c[[1]]==0||c[[2]]==0]; Select[ Range[ 250],not] (* Harvey P. Dale, Dec 15 2012 *)

PARI

is(n, base=3) = #Set(select(sign, digits(n, base)))==1 \\ Rémy Sigrist, Mar 28 2020

PARI

a(n, base=3) = { for (w=0, oo, if (n<=(base-1)*2^w, my (d=1+(n-1)\2^w, k=2^w+(n-1)%(2^w)); return (d*fromdigits(binary(k), base)), n -= (base-1)*2^w)) } \\ Rémy Sigrist, Mar 28 2020