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Search: id:A101779
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| A101779 |
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a(n) = least k such that all of k, 2k+1, 3k+2, ..., nk+n-1 are primes, or 0 if no such k is found. |
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2
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| 2, 2, 3, 5, 5, 154769, 2894219, 2894219, 407874179, 214580145779, 9448481062019, 247236503934419, 2545206711847799, 18178612369988250179, 53792264108455702829
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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a(10) > 3691000000, Robert G. Wilson v (rgwv(AT)rgwv.com), Mar 23 2007
By definition the same as A088651(n)-1 if k exists. It is conjectured k always exists. - a(10)-a(15) from Jens Kruse Andersen (jens.k.a(AT)get2net.dk), May 02 2008
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MATHEMATICA
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f[1] = 2; f[n_] := f[n] = Block[{k = PrimePi@ f[n - 1], p, t = Table[i*p + (i - 1), {i, 2, n}]}, While[p = Prime@k; Union@PrimeQ@t != {True}, k++ ]; p]; Do[ Print[f@n // Timing], {n, 10}] (* Robert G. Wilson v (rgwv@rgwv.com), Mar 23 2007 *)
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CROSSREFS
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Cf. A000040, A005384, A067256, A067257, A067258, A101767, A101768, A101769, A101770.
Cf. A088651.
Sequence in context: A060048 A110699 A035537 this_sequence A137756 A051732 A098382
Adjacent sequences: A101776 A101777 A101778 this_sequence A101780 A101781 A101782
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KEYWORD
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nonn
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AUTHOR
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Jonathan Vos Post (jvospost3(AT)gmail.com) and Ray Chandler (rayjchandler(AT)sbcglobal.net), Jan 13 2005
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EXTENSIONS
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a(10)-a(15) from Jens Kruse Andersen (jens.k.a(AT)get2net.dk), May 02 2008
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