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A214216
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List of minimal forbidden subwords of the Fibonacci word A003482.
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2
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22, 111, 21212, 11211211, 2121121211212, 112112121121121211211, 2121121211211212112121121121211212, 1121121211211212112121121121211211212112121121121211211, 21211212112112121121211211212112112121121211211212112121121121211211212112121121121211212
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OFFSET
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1,1
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COMMENTS
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If S is one of the terms of this sequence, then no word RS can appear as a subword of A003482.
Or, make a list of all words in {1,2}* that do not appear as factors of A003482 and discard any word which has a shorter word on the list as a right factor.
All the terms are palindromes.
Complementing the first and last digits of each term gives (essentially) A214217.
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LINKS
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F. Mignosi, A. Restivo, M. Sciortino, Words and forbidden factors, WORDS (Rouen, 1999). Theoret. Comput. Sci. 273 (2002), no. 1-2, 99--117. MR1872445 (2002m:68096).
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FORMULA
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To get a(n), take A106750(n+2), delete last two digits, producing a palindrome P, say. Then a(n) = 1P1 if n is odd, or 2P2 if n is even.
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EXAMPLE
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A106750(3)=121 -> P=1 -> 111 = a(1).
A106750(4)=12112 -> P=121 -> 2121 = a(2).
A106750(5)=12112121 -> P=121121 -> 11211211 = a(3).
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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