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A224488
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Numbers m such that k*m = Sum_{j|m, j < m} sigma(j), where k >= 1 is an integer.
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2
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4, 10, 42, 90, 2448, 4680, 27144, 117000, 154498509, 222970077, 11049088050, 63554826816
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OFFSET
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1,1
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COMMENTS
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a(13) > 10^11.
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LINKS
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EXAMPLE
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The divisors of 10 smaller than 10 are 1, 2 and 5. Since sigma(1) + sigma(2) + sigma(5) = 10, 10 is in the sequence.
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MATHEMATICA
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Select[Range[2, 120000], Mod[Total@DivisorSigma[1, Most@Divisors@#], #] == 0 &]
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PROG
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(PARI) isok(m) = sumdiv(m, d, if (d!=m, sigma(d))) % m == 0; \\ Michel Marcus, Jul 13 2021
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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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STATUS
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approved
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