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Search: id:A160752
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| A160752 |
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a(n) = the number of sets of (distinct, not necessarily consecutive) positive divisors of n where each set has all of its elements in arithmetic progression, and where each set contains exactly A067131(n) elements. |
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1
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| 1, 1, 1, 3, 1, 1, 1, 6, 3, 6, 1, 1, 1, 6, 1, 10, 1, 2, 1, 15, 6, 6, 1, 2, 3, 6, 6, 1, 1, 4, 1, 15, 6, 6, 6, 2, 1, 6, 6, 1, 1, 2, 1, 15, 3, 6, 1, 3, 3, 15, 6, 15, 1, 3, 6, 2, 6, 6, 1, 1, 1, 6, 15, 21, 6, 3, 1, 15, 6, 28, 1, 4, 1, 6, 2, 15, 6, 2, 1, 2, 10, 6, 1, 2, 6, 6, 6, 28, 1, 10, 1, 15, 6, 6, 6, 4, 1, 15
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OFFSET
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1,4
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COMMENT
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If A067131(n) = 2, then a(n) = d(n)*(d(n)-1)/2, where d(n) is the number of divisors of n.
a(p) = 1 for all primes p.
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EXAMPLE
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The divisors of 18 are 1,2,3,6,9,18. There are 2 sets of these divisors, (1,2,3) and (3,6,9), that have their terms in arithmetic progression and that each have the maximal number (3) of such divisors of 18. So a(18) = 2.
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CROSSREFS
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Cf. A067131.
Sequence in context: A135494 A016566 A096744 this_sequence A080002 A058057 A124372
Adjacent sequences: A160749 A160750 A160751 this_sequence A160753 A160754 A160755
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet (q1qq2qqq3qqqq(AT)yahoo.com), May 25 2009
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jun 15 2009
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