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Search: id:A087634
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| A087634 |
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Primes p such that the equation phi(k) = 4p has a solution, where phi is the totient function. |
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3
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| 2, 3, 5, 7, 11, 13, 23, 29, 37, 41, 43, 53, 67, 73, 79, 83, 89, 97, 113, 127, 131, 139, 163, 173, 179, 191, 193, 199, 233, 239, 251, 277, 281, 293, 307, 359, 373, 409, 419, 431, 433, 443, 487, 491, 499, 509, 577, 593, 619, 641, 653, 659, 673, 683, 709, 719, 727
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Except for p=2, the complement of A043297. Note that for primes p < 1000, we need to check for solutions k < 18478. The equation phi(k) = 2p has solutions for Sophie Germain primes, A005384
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LINKS
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Eric Weisstein's World of Mathematics, Totient Function
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MATHEMATICA
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t=Table[EulerPhi[n], {n, 3, 20000}]; Union[Select[t, Mod[ #, 4]==0&&PrimeQ[ #/4]&& #/4<1000&]/4]
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CROSSREFS
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Cf. A005384, A043297.
Adjacent sequences: A087631 A087632 A087633 this_sequence A087635 A087636 A087637
Sequence in context: A067910 A075430 A095080 this_sequence A038970 A079149 A024694
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KEYWORD
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nonn
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AUTHOR
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T. D. Noe (noe(AT)sspectra.com), Oct 24 2003
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