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Search: id:A123371
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| A123371 |
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Smallest number k>1 such that (1 + Sum[ i^(2n - 1), {i,1,k} ]) is prime, or 0 if no such number k exists. |
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+0
1
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| 3, 3, 3, 4, 35, 16, 7, 4, 11, 55, 112, 183, 36, 51, 23, 56, 8, 16, 32, 28, 115, 135, 44, 15, 28, 111, 43, 364, 80, 44, 144, 59, 3, 48, 68, 75, 63, 48, 175, 228, 416, 39, 163, 251, 7, 331, 35, 4, 412, 4, 152, 63, 483, 11, 239, 75, 47, 11, 32, 3, 163, 211, 44, 40, 155, 555
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Conjecture: a(n)>0 exists for all n.
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EXAMPLE
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a(1) = 3 because 1 + Sum[ i, {i,1,3} ] = 1 + (1 + 2 + 3) = 7 is prime and 1 + (1 + 2) = 4 is composite.
a(2) = 3 because 1 + Sum[ i^3, {i,1,3} ] = 1 + (1^3 + 2^3 + 3^3) = 37 is prime and 1 + (1^3 + 2^3) = 10 is composite.
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CROSSREFS
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Sequence in context: A091849 A035567 A108688 this_sequence A011277 A084742 A049613
Adjacent sequences: A123368 A123369 A123370 this_sequence A123372 A123373 A123374
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KEYWORD
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hard,nonn
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AUTHOR
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Alexander Adamchuk (alex(AT)kolmogorov.com), Nov 09 2006
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