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A068365
Numbers k such that sigma(k) = phi((prime(k)+prime(k+1))/2).
0
14, 24, 308, 474, 690, 1242, 2970, 9690, 10340, 13110, 18270, 26400, 161880
OFFSET
1,1
COMMENTS
Are there any odd numbers in the sequence?
There are no more terms up to 2500000. - Rick L. Shepherd, Aug 29 2002
No more terms below 3*10^9. - Amiram Eldar, Feb 01 2024
MATHEMATICA
Select[Range[2, 162000], DivisorSigma[1, #]==EulerPhi[ (Prime[ #]+ Prime[ #+1])/2]&] (* Harvey P. Dale, Aug 23 2021 *)
PROG
(PARI) for(n=2, 2500000, if(sigma(n)==eulerphi((prime(n)+prime(n+1))/2), print1(n, ", ")))
CROSSREFS
Sequence in context: A211323 A141838 A140499 * A154038 A366960 A061923
KEYWORD
nonn,more
AUTHOR
Benoit Cloitre, Feb 28 2002
EXTENSIONS
More terms from Rick L. Shepherd, Aug 29 2002
STATUS
approved