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A165500
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Maximum length of arithmetic progression starting at n such that each term k has tau(k) = tau(n).
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2
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1, 2, 3, 2, 5, 3, 7, 4, 2, 5, 11, 3, 13, 7, 6, 2, 17, 3, 19, 5, 7, 11
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OFFSET
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1,2
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COMMENTS
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Implicitly, we require the difference d of the arithmetic progression to be positive.
a(n) <= n for all n.
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LINKS
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Table of n, a(n) for n=1..22.
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EXAMPLE
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For n=4, tau(n)=3 so each term of the arithmetic progression must be the square of a prime. The difference d must be odd for n+d to qualify, in which case n+2d is even and does not qualify; so a(4)=2 is an upper bound.
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CROSSREFS
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Cf. A165498, A165501, A088430.
Sequence in context: A331634 A139421 A219964 * A072505 A095163 A033677
Adjacent sequences: A165497 A165498 A165499 * A165501 A165502 A165503
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KEYWORD
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hard,nonn,more
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AUTHOR
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Hugo van der Sanden, Sep 21 2009, Oct 09 2009
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EXTENSIONS
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Extended to n=22 (taking advantage of A088430 for n=19) by Hugo van der Sanden, Jun 02 2015
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STATUS
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approved
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