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

0,3

Comments

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

Links

Table of n, a(n) for n=0..60.

Formula

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

Mathematica

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

Crossrefs

Sequence in context: A236842 A236860 A031942 * A317044 A267302 A023799

Adjacent sequences: A043087 A043088 A043089 * A043091 A043092 A043093

Keyword

nonn,base

Author

Clark Kimberling

Status

approved