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A068366 Numbers k such that phi(sigma(k)+k) = sigma(k). 1
1, 7, 15, 127, 267, 315, 495, 621, 969, 1155, 1917, 5649, 7515, 12267, 14911, 17271, 22347, 26265, 28671, 30549, 31641, 32895, 45195, 48093, 56697, 60801, 64923, 77409, 79827, 82731, 83559, 116745, 123387, 172653, 173901, 179223, 184869 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,2
COMMENTS
Are there any even values in the sequence?
LINKS
MATHEMATICA
q[n_] := Module[{s = DivisorSigma[1, n]}, EulerPhi[s + n] == s]; Select[Range[10^5], q] (* Amiram Eldar, Dec 11 2023 *)
PROG
(PARI) for(n=1, 300000, if(eulerphi(sigma(n)+n)==sigma(n), print1(n, ", ")))
CROSSREFS
Sequence in context: A032004 A032018 A243470 * A156499 A137881 A042725
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Feb 28 2002
EXTENSIONS
More terms from Rick L. Shepherd, Apr 22 2002
STATUS
approved

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Last modified April 13 20:16 EDT 2024. Contains 371645 sequences. (Running on oeis4.)