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A069146
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Numbers m such that m = sigma(abs(k)) - 3k, where k = sigma(m) - 3m.
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1
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1248, 1596, 28272, 30240, 32760, 463296, 2178540, 12865770, 23569920, 30998250, 45532800, 142990848, 1379454720, 1912369152, 2623977450, 43861478400, 66433720320, 153003540480, 403031236608, 489622536192, 704575228896
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OFFSET
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1,1
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COMMENTS
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1.5*10^12 < a(22) <= 7834005405696. If 2^k-1 > 3 is a prime (A000023), then 2^(k-1)*3*19*(2^k-1) is a term. - Giovanni Resta, Dec 11 2019
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LINKS
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EXAMPLE
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Let n = 1248. The sum of the divisors of n is 3528, so k = 3528 - 3*1248 = -216. The sum of the divisors of 216 is 600 and 600 - 3*(-216) = 1248, so 1248 is in the sequence.
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MATHEMATICA
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Select[Range[5*10^5], DivisorSigma[1, Abs[(k = DivisorSigma[1, #] - 3#)]] -3k == # &] (* Amiram Eldar, Dec 11 2019 *)
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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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