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A097645
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Numbers k such that k = sigma(phi(k) + pi(k)).
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2
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1, 6, 54, 78, 1296, 1482, 6480, 6552, 14040, 20160, 36936, 1273896
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OFFSET
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1,2
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COMMENTS
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Does this sequence have any odd terms > 1? There is no other term up to 3*10^7.
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LINKS
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EXAMPLE
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1273896 is in the sequence because pi(1273896) = 98190, phi(1273896) = 391680, and sigma(98190+391680) = 1273896.
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MATHEMATICA
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Do[If[n==DivisorSigma[1, EulerPhi[n]+PrimePi[n]], Print[n]], {n, 10000000}].
Parallelize[While[True, If[DivisorSigma[1, EulerPhi[n]+PrimePi[n]]==n, Print[n]]; n++]; n], n] (* J.W.L. (Jan) Eerland, Dec 25 2021 *)
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PROG
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(PARI) isok(k) = k == sigma(eulerphi(k) + primepi(k)); \\ Michel Marcus, Dec 25 2021
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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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