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Search: id:A139719
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| A139719 |
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A number n is included if k + n/k divides n for at least one divisor k of n. |
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+0
3
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| 4, 16, 18, 36, 48, 64, 72, 100, 144, 150, 162, 180, 192, 196, 256, 288, 294, 324, 400, 432, 448, 450, 484, 490, 576, 588, 600, 648, 676, 720, 768, 784, 882, 900, 960, 1024, 1134, 1152, 1156, 1176, 1200, 1210, 1296, 1350, 1444, 1458, 1584, 1600, 1620, 1728
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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All terms are even. All even perfect squares are included. If n is included, then 4n is also included.
Also the set of all numbers n of the form n = r*s*(r+s)^2*t^2 with positive integers r,s,t; if one additionally requires (r,s) = 1 and r <= s, then there is exactly one such representation for each n. [From Hagen von Eitzen (math(AT)von-eitzen.de), Jul 22 2009]
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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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72 is included because 6 is a divisor of 72 and (6 + 72/6) = 18 divides 72.
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CROSSREFS
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Cf. A139718.
Sequence in context: A037409 A034121 A166620 this_sequence A117102 A077476 A146510
Adjacent sequences: A139716 A139717 A139718 this_sequence A139720 A139721 A139722
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KEYWORD
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nonn
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AUTHOR
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Leroy Quet May 01 2008
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EXTENSIONS
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Extended by Ray Chandler (rayjchandler(AT)sbcglobal.net), Jul 01 2009
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