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A062514
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Numbers k such that sigma(phi(k)) is a prime.
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7
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3, 4, 5, 6, 8, 10, 12, 17, 32, 34, 40, 48, 60, 85, 128, 136, 160, 170, 192, 204, 240, 4369, 8192, 8224, 8704, 8738, 10240, 10280, 10880, 12288, 12336, 13056, 15360, 15420, 16320, 65537, 131072, 131074, 131584, 139264, 139808, 163840, 164480, 174080
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OFFSET
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1,1
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COMMENTS
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Numbers k such that A062402(k) is prime.
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LINKS
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EXAMPLE
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Phi(174080)=65536. Sigma(65536) = 131071, a prime.
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PROG
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(PARI) je=[]; for(n=1, 300000, s=sigma(eulerphi(n)); if(isprime(s), je=concat(je, n))); je
(PARI) { n=0; for (m=1, 10^9, if(isprime(sigma(eulerphi(m))), write("b062514.txt", n++, " ", m); if (n==73, break)) ) } \\ Harry J. Smith, Aug 08 2009
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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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STATUS
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approved
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