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A078729
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a(n) = the least positive integer k such that (k+1)(k+2)...(k+n) + 1 is prime, if such k exists; otherwise, = 0.
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0
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1, 1, 2, 0, 2, 2, 3, 3, 5, 1, 2, 9, 4, 2, 8, 5, 5, 3, 4, 7, 5, 6, 18, 24, 10, 1, 11, 2, 8, 22, 6, 6, 38, 4, 6, 1, 13, 4, 77, 1, 2, 14, 18, 11, 16, 5, 2, 13, 7, 20, 22, 16, 13, 39, 15, 5, 7, 12, 14, 4, 14, 81, 45, 50, 38, 42, 5, 10, 60, 56, 15, 1, 45, 25, 53, 1, 23, 12, 3, 61, 30, 68, 26, 154
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OFFSET
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1,3
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COMMENTS
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(k+1)(k+2)(k+3)(k+4) + 1 = (k^2 + 5x + 5)^2, which is never prime. Hence a(4) = 0. Is this the only zero term? - Benoit Cloitre, Jan 16, 2003
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LINKS
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Table of n, a(n) for n=1..84.
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EXAMPLE
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k=2 is the least positive integer such that (k+1)(k+2)(k+3) + 1 is prime, so a(3) = 2.
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CROSSREFS
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Sequence in context: A022830 A035663 A117192 * A029906 A094907 A158380
Adjacent sequences: A078726 A078727 A078728 * A078730 A078731 A078732
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Jan 08 2003
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EXTENSIONS
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More terms from Benoit Cloitre, Jan 16, 2003
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STATUS
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approved
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