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A137258
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Primes p that satisfy s-t < 0 where s = sigma(2*p+1) mod phi(p) and t = sigma(2*p+1) mod p.
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0
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3, 5, 7, 17, 19, 139, 157, 577, 1201, 27361, 530401, 2513281, 7183201, 407817217
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OFFSET
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1,1
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COMMENTS
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The function sigma(n) is the sum of positive divisors function and the function phi(n) is the Euler totient function.
The positive values of s-t for primes p<2000 are 0, 2, 3, 4.
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LINKS
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PROG
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(PARI) p=1; for(i=1, 10^9, p=nextprime(p+1); s=sigma(2*p+1); if(s%(p-1)<s%p, print(p))) /* Donovan Johnson, Feb 15 2013 */
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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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Juan Lopez Gonzalez (juan.lopezg(AT)estudiante.uam.es), Apr 25 2008
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EXTENSIONS
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STATUS
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approved
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