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A067893
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Nonprimes k such that tau(k)*sigma(k) < prime(k) where tau(k) = A000005(k) and sigma(k) = A000203(k).
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1
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1, 25, 49, 77, 85, 91, 95, 115, 119, 121, 123, 125, 129, 133, 141, 143, 145, 155, 159, 161, 169, 177, 183, 185, 187, 194, 201, 202, 203, 205, 206, 209, 213, 214, 215, 217, 218, 219, 221, 226, 235, 237, 247, 249, 253, 254, 259, 262, 265, 267, 274, 278, 287
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Select[Range[300], !PrimeQ[#]&&DivisorSigma[0, #]DivisorSigma[1, #]<Prime[ #]&](* Harvey P. Dale, Nov 09 2017 *)
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PROG
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(PARI) isok(k) = !isprime(k) && (numdiv(k)*sigma(k) < prime(k)); \\ Michel Marcus, Jul 18 2019
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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