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A130838 Sorted list of strings that can be obtained by starting with 12 and repeatedly doubling any substring in place. 2
12, 112, 122, 1112, 1122, 1212, 1222, 11112, 11122, 11212, 11222, 12112, 12122, 12212, 12222, 111112, 111122, 111212, 111222, 112112, 112122, 112212, 112222, 121112, 121122, 121212, 121222, 122112, 122122, 122212, 122222 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

The list contains 2^(n-2) strings of length n, namely 1{1,2}^(n-2)2, for n >= 2.

LINKS

Table of n, a(n) for n=1..31.

Index entries for doubling substrings

CROSSREFS

Sequence in context: A199357 A293872 A044344 * A225189 A044725 A265948

Adjacent sequences:  A130835 A130836 A130837 * A130839 A130840 A130841

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Feb 22 2008

STATUS

approved

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Last modified June 14 15:36 EDT 2021. Contains 345025 sequences. (Running on oeis4.)