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A279798
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Largest prime factor of 78557*2^n + 1.
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0
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67, 104743, 8609, 281, 521, 1163, 1436471, 12391, 136343, 1483, 23663, 727, 10453, 2029, 135481883, 7429021, 2059324621, 6864415403, 3716857, 9629, 451358821, 51782483, 62504399, 439322585771, 63337, 128110399, 42209, 59569669, 111486983, 10936129, 31585821557
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OFFSET
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1,1
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COMMENTS
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a(n) <= A258073(n) / A258091(n).
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LINKS
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Table of n, a(n) for n=1..31.
Wikipedia, Sierpinski Number
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FORMULA
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a(n) = A006530(A258073(n)).
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EXAMPLE
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78557 * 2^1 + 1 = 157115 = 5 * 7 * 67^2. So a(1) = 67.
78557 * 2^2 + 1 = 314229 = 3 * 104743. So a(2) = 104743.
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MATHEMATICA
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Table[FactorInteger[2^n * 78557 + 1][[-1, 1]], {n, 30}] (* Alonso del Arte, Jan 01 2017 *)
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PROG
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(PARI) a(n) = my(k=78557*2^n+1); factor(k)[omega(k), 1] \\ Felix Fröhlich, Jan 01 2017
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CROSSREFS
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Cf. A002587, A258073, A258091.
Sequence in context: A144940 A211962 A263463 * A191941 A087536 A281888
Adjacent sequences: A279795 A279796 A279797 * A279799 A279800 A279801
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KEYWORD
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nonn
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AUTHOR
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Seiichi Manyama, Dec 19 2016
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STATUS
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approved
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