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 A107815 Primes p such that sigma(k) = phi(prime(k)-1), where p = prime(k). 2
 2, 17, 67, 211, 631, 1051, 1811, 1951, 2287, 2791, 3331, 7297, 10099, 13597, 15739, 19717, 21169, 22153, 41341, 85933, 400051, 2251201, 2991253, 3051751, 4244791, 5713891 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS a(n) = prime(A067651(n)). Values of k are in A067651, values of sigma(k) are in A107816. LINKS EXAMPLE a(3) = prime(A067651(3)) = prime(19) = 67. PROG (PARI) m=400000; for(n=1, m, p=prime(n); if(sigma(n)==eulerphi(p-1), print1(p, ", "))) CROSSREFS Cf. A067651, A107816. Sequence in context: A037420 A034721 A281708 * A042803 A182876 A056074 Adjacent sequences:  A107812 A107813 A107814 * A107816 A107817 A107818 KEYWORD nonn,more AUTHOR Klaus Brockhaus, May 24 2005 STATUS approved

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Last modified July 25 19:34 EDT 2021. Contains 346291 sequences. (Running on oeis4.)