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A067680
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Numbers k such that sigma(2k + 2) = 4k.
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1
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6, 21, 54, 75, 441, 1071, 4191, 9315, 58311, 4197375, 7685151, 36997695, 268460031, 1073790975, 17180065791, 13517087570210304, 18014398710808575, 288230376957018111
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OFFSET
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1,1
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COMMENTS
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LINKS
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PROG
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(PARI) isok(k) = sigma(2*k+2) == 4*k; \\ Michel Marcus, Apr 06 2020
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CROSSREFS
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KEYWORD
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nonn,more
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AUTHOR
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EXTENSIONS
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a(9) from Benoit Cloitre and Neven Juric (neven.juric(AT)apis-it.hr), May 21 2004
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STATUS
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approved
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