A043089 Every string of 2 consecutive base-3 digits contains exactly 2 distinct numbers.

0, 1, 2, 3, 5, 6, 7, 10, 11, 15, 16, 19, 20, 21, 23, 30, 32, 33, 34, 46, 47, 48, 50, 57, 59, 60, 61, 64, 65, 69, 70, 91, 92, 96, 97, 100, 101, 102, 104, 138, 140, 141, 142, 145, 146, 150, 151, 172, 173, 177, 178, 181, 182, 183, 185, 192

Offset: 0

Author

Clark Kimberling

Keywords

• nonn
• base

Comments

Essentially the same as A031941. - R. J. Mathar, Oct 20 2008

Links

• Harvey P. Dale, Table of n, a(n) for n = 0..1000

Crossrefs

Cf. A031941.

Programs

Mathematica

Select[Range[0,200],FreeQ[Differences[IntegerDigits[#,3]],0]&] (* Harvey P. Dale, Feb 25 2022 *)

PARI

a(n, base=3) = { for (b=0, oo, if (n <= (base-1)*2^b, my (v=ceil(n/2^b), p=(n-1)%(2^b)); while (b>0, v=base*v+vecsort([(v-1)%base, (v+1)%base])[1+bittest(p,b--)];); return (v), n -= (base-1)*2^b);); } \\ Rémy Sigrist, Sep 15 2022