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A107815
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Primes p such that sigma(k) = phi(prime(k)-1), where p = prime(k).
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2
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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; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n) = prime(A067651(n)).
Values of k are in A067651, values of sigma(k) are in A107816.
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EXAMPLE
| a(3) = prime(A067651(3)) = prime(19) = 67.
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PROG
| (PARI) m=400000; for(n=1, m, p=prime(n); if(sigma(n)==eulerphi(p-1), print1(p, ", ")))
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CROSSREFS
| Cf. A067651, A107816.
Sequence in context: A176581 A037420 A034721 * A042803 A182876 A056074
Adjacent sequences: A107812 A107813 A107814 * A107816 A107817 A107818
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KEYWORD
| nonn,more
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AUTHOR
| Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 24 2005
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