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A067788
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Numbers n such that sigma(n) - phi(n) = pi(n).
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0
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1, 3, 49, 437, 11509, 3029573, 15714799, 15715171, 312616663, 45764089927, 2002330897321
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OFFSET
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1,2
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COMMENTS
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pi(n) denotes the number of positive primes not exceeding n.
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LINKS
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EXAMPLE
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sigma(49) - phi(49) = 15 = pi(49), so 49 is a term of the sequence.
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MATHEMATICA
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Select[Range[10^5], DivisorSigma[1, #] - EulerPhi[#] == PrimePi[#] &] (* Giovanni Resta, Mar 31 2017 *)
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PROG
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(PARI) isok(n) = sigma(n) - eulerphi(n) == primepi(n); \\ Michel Marcus, Oct 13 2014
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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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