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Search: id:A133780
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| A133780 |
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Irregular array: n-th row lists the "non-isolated divisors" of (2n). A positive divisor, k, of n is non-isolated if (k-1) or (k+1) also divides n. |
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3
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| 1, 2, 1, 2, 1, 2, 3, 1, 2, 1, 2, 1, 2, 3, 4, 1, 2, 1, 2, 1, 2, 3, 1, 2, 4, 5, 1, 2, 1, 2, 3, 4, 1, 2, 1, 2, 1, 2, 3, 5, 6, 1, 2, 1, 2, 1, 2, 3, 4, 1, 2, 1, 2, 4, 5, 1, 2, 3, 6, 7, 1, 2, 1, 2, 1, 2, 3, 4, 1, 2, 1, 2, 1, 2, 3, 1, 2, 7, 8, 1, 2, 1, 2, 3, 4, 5, 6, 1, 2, 1, 2, 1, 2, 3, 1, 2, 1, 2, 1, 2, 3, 4, 8, 9, 1
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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No odd integer has any non-isolated divisors. The number of terms in the n-th row of the array is A132747(2n).
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EXAMPLE
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The positive divisors of 20 are 1,2,4,5,10,20. Of these, 1 and 2 are adjacent, and 4 and 5 are adjacent. So the non-isolated divisors of 20 are 1,2,4,5.
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CROSSREFS
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Cf. A133779, A132747, A132748.
Sequence in context: A102566 A134156 A067815 this_sequence A080237 A136109 A105265
Adjacent sequences: A133777 A133778 A133779 this_sequence A133781 A133782 A133783
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KEYWORD
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nonn,tabf
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AUTHOR
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Leroy Quet (q1qq2qqq3qqqq(AT)yahoo.com), Sep 23 2007
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jun 24 2008
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