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Search: id:A136529
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| A136529 |
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a(n) = the smallest possible number of positive divisors of the sum of any two distinct positive divisors of n. |
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+0
2
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| 2, 3, 2, 4, 2, 4, 2, 3, 2, 6, 2, 4, 2, 3, 2, 6, 2, 6, 2, 3, 2, 8, 2, 4, 2, 3, 2, 8, 2, 6, 2, 3, 2, 4, 2, 4, 2, 3, 2, 8, 2, 6, 2, 3, 2, 10, 2, 4, 2, 3, 2, 8, 2, 4, 2, 3, 2, 12, 2, 4, 2, 3, 2, 4, 2, 6, 2, 3, 2, 12, 2, 4, 2, 3, 2, 4, 2, 10, 2, 3, 2, 12, 2, 4, 2, 3, 2, 12, 2, 4, 2, 3, 2, 4, 2, 6, 2, 3, 2, 8, 2, 8
(list; graph; listen)
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OFFSET
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2,1
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COMMENT
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There are d(n)*(d(n)-1)/2 sums of pairs of distinct positive divisors of n, where d(n) = number of positive divisors of n.
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LINKS
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Leroy Quet, Home Page (listed in lieu of email address)
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EXAMPLE
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The positive divisors of 6 are 1,2,3,6. Letting d(m) = the number of positive divisors of m: d(1+2)=2; d(1+3)=3; d(1+6)=2; d(2+3)=2; d(2+6)=4; d(3+6)=3. The least of these values is 2, so a(6) = 2.
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PROGRAM
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(PARI) { a(n) = d=divisors(n); m=numdiv(n+1); for(i=1, #d, for(j=i+1, #d, m=min(m, numdiv(d[i]+d[j])); )); m } [From Max Alekseyev (maxale(AT)gmail.com), Apr 27 2009]
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CROSSREFS
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Cf. A136528.
Sequence in context: A025477 A080189 A076399 this_sequence A113982 A101743 A060937
Adjacent sequences: A136526 A136527 A136528 this_sequence A136530 A136531 A136532
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet Jan 03 2008
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EXTENSIONS
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Extended by Max Alekseyev (maxale(AT)gmail.com), Apr 27 2009
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