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 A067224 Numbers k such that phi(5k-1) = sigma(k). 2
 5225, 20405, 181685, 210395, 302375, 302445, 524975, 1469555, 1563485, 1748855, 2791085, 3097055, 4418375, 4542065, 4735115, 5482235, 5567705, 5568615, 5683205, 5753405, 6457055, 7363013, 7531205, 8016435, 8043875, 9534185, 10511345, 10790325, 11504405 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Are there any terms not congruent to 5 in the sequence? a(22) = 7363013 is the first example. - Charles R Greathouse IV, Jan 29 2012 LINKS Table of n, a(n) for n=1..29. MATHEMATICA Select[Range[10^6], EulerPhi[5*# - 1] == DivisorSigma[1, #] &] (* Amiram Eldar, May 09 2022 *) PROG (PARI) for(n=1, 1e8, if(sigma(n)==eulerphi(5*n-1), print1(n", "))) \\ Charles R Greathouse IV, Jan 29 2012 CROSSREFS Cf. A000010, A000203, A067226, A067235. Sequence in context: A231113 A289514 A031616 * A204139 A237408 A235296 Adjacent sequences: A067221 A067222 A067223 * A067225 A067226 A067227 KEYWORD nonn AUTHOR Benoit Cloitre, Feb 20 2002 EXTENSIONS a(8)-a(29) from Donovan Johnson, Jan 29 2012 STATUS approved

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Last modified April 16 04:17 EDT 2024. Contains 371696 sequences. (Running on oeis4.)