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A039778
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phi(n) is equal to the sum of prime factors and exponents of n+1.
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0
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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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phi(38)=18, 39=3^1*13^1, 3+1+13+1=18.
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MATHEMATICA
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Select[Range[30000], EulerPhi[#] == Plus @@ Flatten@ FactorInteger[# + 1] &] (* Giovanni Resta, Jun 11 2016 *)
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PROG
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(PARI) isok(n) = (f = factor(n+1)) && (sum(i=1, #f~, f[i, 2]) + sum(i=1, #f~, f[i, 1]) == eulerphi(n)); \\ Michel Marcus, Jun 03 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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STATUS
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approved
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