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A233189
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Numbers n such that phi(n) + pi(n) = n+1.
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0
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3, 9, 55, 65, 95, 145, 155, 185, 205, 2779, 2863, 21199, 174691, 174779, 1277809, 1301989, 1302457, 1930091, 2554873, 8170013, 70111213, 70111247, 514269523, 514269599, 27788312339, 341964217733, 358200797989, 763730325367, 1975633764583
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OFFSET
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1,1
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COMMENTS
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LINKS
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EXAMPLE
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a(3)= 55: n= 55: phi(n)+pi(n)= 40+16= 56 which equals n+1= 55+1= 56.
a(4)= 65: n= 65: phi(n)+pi(n)= 48+18= 66 which equals n+1= 65+1= 66.
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MAPLE
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with(numtheory): KD:= proc() local a, b; a:= n+1; b:=phi(n) +pi(n); if a=b then RETURN (n); fi; end: seq(KD(), n=1..10000000);
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MATHEMATICA
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Do[If [ PrimePi[n]+EulerPhi[n] == n+1, Print[n]], {n, 100000000}]
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PROG
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(PARI) isok(n) = eulerphi(n)+primepi(n) == n + 1; \\ Michel Marcus, Apr 01 2017
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CROSSREFS
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Cf. A000203 (sigma(n): sum of divisors of n).
Cf. A000720 (pi(n): number of primes <= n).
Cf. A037170 (numbers n: pi(n) + phi(n)= n).
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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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