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A281663
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Refactorable numbers that are not the sum of two refactorable numbers.
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1
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OFFSET
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1,2
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COMMENTS
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Is this sequence finite?
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LINKS
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Table of n, a(n) for n=1..7.
S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999.
Joshua Zelinsky, Tau Numbers: A Partial Proof of a Conjecture and Other Results , Journal of Integer Sequences, Vol. 5 (2002), Article 02.2.8
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EXAMPLE
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40 is a term because 40 is a refactorable number and there is no partition of 40 into two refactorable parts.
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PROG
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(PARI) isrefac(n) = (n%numdiv(n))==0;
isok(n) = isrefac(n) && (sum(k=1, n\2, isrefac(k) && isrefac(n-k)) == 0); \\ Michel Marcus, Jan 26 2017
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CROSSREFS
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Cf. A033950, A172398, A280634.
Sequence in context: A024604 A025103 A307652 * A092179 A269726 A032410
Adjacent sequences: A281660 A281661 A281662 * A281664 A281665 A281666
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KEYWORD
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nonn,more
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AUTHOR
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Altug Alkan, Jan 26 2017
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STATUS
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approved
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