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A043090 Every string of 2 consecutive base 4 digits contains exactly 2 distinct numbers. 8
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 (list; graph; refs; listen; history; text; internal format)
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

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Last modified March 23 14:17 EDT 2019. Contains 321431 sequences. (Running on oeis4.)