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Search: id:A061599
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| A061599 |
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Primes p such that the greatest prime divisor of p-1 is 5. |
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3
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| 11, 31, 41, 61, 101, 151, 181, 241, 251, 271, 401, 541, 601, 641, 751, 811, 1201, 1601, 1621, 1801, 2161, 2251, 3001, 4001, 4051, 4801, 4861, 6481, 7681, 8101, 8641, 9001, 9601, 9721, 11251, 14401, 15361, 16001, 19441, 21601, 21871, 22501, 23041, 24001
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Prime numbers n for which cos(2pi/n) is an algebraic number of 5-th degree. - Artur Jasinski (grafix(AT)csl.pl), Dec 13 2006
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LINKS
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Harry J. Smith, Table of n, a(n) for n=1,...,200
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FORMULA
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Primes of form (2^a).(3^b).(5^c)+1.
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MATHEMATICA
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Do[If[Take[FactorInteger[EulerPhi[2n + 1]][[ -1]], 1] == {5} && PrimeQ[2n + 1], Print[2n + 1]], {n, 1, 10000}] - Artur Jasinski (grafix(AT)csl.pl), Dec 13 2006
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PROGRAM
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(PARI) { default(primelimit, 167772161); n=0; forprime (p=3, 167772161, f=factor(p - 1)~; if (f[1, length(f)]==5, write("b061599.txt", n++, " ", p)) ) } [From Harry J. Smith (hjsmithh(AT)sbcglobal.net), Jul 25 2009]
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CROSSREFS
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The 3rd in a family of sequences after A019434(=Fermat-primes) and A058383.
Cf. A019434, A058383, A023503, A034694, A006530, A006093, A035095, A000040.
Cf. A004729, A058383, A125867-A125875, A024899.
Sequence in context: A040979 A089347 A040985 this_sequence A153128 A040971 A138656
Adjacent sequences: A061596 A061597 A061598 this_sequence A061600 A061601 A061602
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KEYWORD
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nonn
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AUTHOR
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Labos E. (labos(AT)ana.sote.hu), Jun 13 2001
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