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A044353 Numbers n such that string 2,1 occurs in the base 10 representation of n but not of n-1. 0
21, 121, 210, 221, 321, 421, 521, 621, 721, 821, 921, 1021, 1121, 1210, 1221, 1321, 1421, 1521, 1621, 1721, 1821, 1921, 2021, 2100, 2210, 2221, 2321, 2421, 2521, 2621, 2721, 2821, 2921, 3021, 3121, 3210, 3221, 3321, 3421 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

LINKS

Table of n, a(n) for n=1..39.

MATHEMATICA

Select[Range[3500], MemberQ[Partition[IntegerDigits[#], 2, 1], {2, 1}] && !MemberQ[Partition[IntegerDigits[#-1], 2, 1], {2, 1}]&] (* Harvey P. Dale, Sep 24 2011 *)

CROSSREFS

Sequence in context: A074088 A245031 A316713 * A044734 A325484 A200888

Adjacent sequences:  A044350 A044351 A044352 * A044354 A044355 A044356

KEYWORD

nonn,base

AUTHOR

Clark Kimberling

STATUS

approved

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Last modified May 28 04:00 EDT 2020. Contains 334671 sequences. (Running on oeis4.)