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A171260
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Numbers n such that sigma(n) = 15*phi(n) (where sigma=A000203, phi=A000010).
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5
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840, 11880, 12180, 25080, 32130, 67830, 79170, 172260, 282744, 312840, 363660, 569160, 596904, 634410, 696696, 843780, 846090, 959310, 996840, 1119690, 1201560, 1402440, 1542840, 1607340, 1929312, 2104440, 2247210, 2363790, 3309240, 3368040, 3883680
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OFFSET
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1,1
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LINKS
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MATHEMATICA
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Select[Range[10^6], DivisorSigma[1, #] == 15 * EulerPhi[#] &] (* Amiram Eldar, Dec 04 2019 *)
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PROG
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(PARI) for(k=1, 3e6, sigma(k) - 15*eulerphi(k) || print1(k", "));
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CROSSREFS
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Cf. A062699, A068391, A068390, A136547, A104900, A136540, A104901, A163667, A171256, A171257, A104902, A171258, A171259, A104903.
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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