A043090 Every string of 2 consecutive base 4 digits contains exactly 2 distinct numbers.

0, 1, 2, 3, 4, 6, 7, 8, 9, 11, 12, 13, 14, 17, 18, 19, 24, 25, 27, 28, 29, 30, 33, 34, 35, 36, 38, 39, 44, 45, 46, 49, 50, 51, 52, 54, 55, 56, 57, 59, 68, 70, 71, 72, 73, 75, 76, 77, 78, 97, 98, 99, 100, 102, 103, 108, 109, 110, 113, 114, 115

Offset: 0

Author

Clark Kimberling

Keywords

• nonn
• base

Comments

No two consecutive base 4 digits are the same. - Harvey P. Dale, Nov 24 2018

Programs

Mathematica

Select[Range[0,120],SequenceCount[IntegerDigits[#,4],{x_,x_}]==0&] (* Requires Mathematica version 10 or later *) (* Harvey P. Dale, Nov 24 2018 *)

Formula

A031942 UNION {0}. [From R. J. Mathar, Oct 20 2008]