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A068365
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Numbers k such that sigma(k) = phi((prime(k)+prime(k+1))/2).
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0
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14, 24, 308, 474, 690, 1242, 2970, 9690, 10340, 13110, 18270, 26400, 161880
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OFFSET
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1,1
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COMMENTS
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Are there any odd numbers in the sequence?
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LINKS
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MATHEMATICA
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Select[Range[2, 162000], DivisorSigma[1, #]==EulerPhi[ (Prime[ #]+ Prime[ #+1])/2]&] (* Harvey P. Dale, Aug 23 2021 *)
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PROG
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(PARI) for(n=2, 2500000, if(sigma(n)==eulerphi((prime(n)+prime(n+1))/2), print1(n, ", ")))
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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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