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Search: id:A107815
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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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+0
3
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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; listen)
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OFFSET
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1,1
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COMMENT
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a(n) = prime(A067651(n)).
Values of k are in A067651, values of sigma(k) are in A107816.
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EXAMPLE
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a(3) = prime(A067651(3)) = prime(19) = 67.
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PROGRAM
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(PARI) m=400000; for(n=1, m, p=prime(n); if(sigma(n)==eulerphi(p-1), print1(p, ", ")))
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CROSSREFS
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Cf. A067651, A107816.
Sequence in context: A002430 A037420 A034721 this_sequence A042803 A056074 A054568
Adjacent sequences: A107812 A107813 A107814 this_sequence A107816 A107817 A107818
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KEYWORD
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nonn,more
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AUTHOR
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Klaus Brockhaus (klaus-brockhaus(AT)t-online.de), May 24 2005
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