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A125045
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Odd primes generated recursively: a(1) = 3, a(n) = Min {p is prime; p divides Q+2}, where Q is the product of previous terms in the sequence.
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19
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3, 5, 17, 257, 65537, 641, 7, 318811, 19, 1747, 12791, 73, 90679, 67, 59, 113, 13, 41, 47, 151, 131, 1301297155768795368671, 20921, 1514878040967313829436066877903, 5514151389810781513, 283, 1063, 3027041
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OFFSET
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1,1
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COMMENTS
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The first five terms comprise the known Fermat primes: A019434.
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LINKS
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Sean A. Irvine, Table of n, a(n) for n = 1..64
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EXAMPLE
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a(7) = 7 is the smallest prime divisor of 3 * 5 * 17 * 257 * 65537 * 641 + 2 = 2753074036097 = 7 * 11 * 37 * 966329953.
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MATHEMATICA
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a={3}; q=1;
For[n=2, n<=20, n++,
q=q*Last[a];
AppendTo[a, Min[FactorInteger[q+2][[All, 1]]]];
];
a (* Robert Price, Jul 16 2015 *)
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CROSSREFS
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Cf. A000945, A019434, A057204-A057208, A051308-A051335, A124984-A124993, A125037-A125045.
Sequence in context: A078726 A019434 A164307 * A093179 A067387 A050922
Adjacent sequences: A125042 A125043 A125044 * A125046 A125047 A125048
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KEYWORD
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nonn
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AUTHOR
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Nick Hobson (http://www.qbyte.org/puzzles/), Nov 18 2006
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STATUS
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approved
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