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A125504
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Smallest number k such that the numerator of alternating generalized harmonic number H'(k,n) = Sum[ (-1)^(i+1) * 1/i^n, {i,1,k} ] is a prime.
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0
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3, 2, 2, 3, 2, 19, 2, 146, 87, 3, 16, 3, 2, 249, 15, 87, 2, 699, 2
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| a(n) = 2 for n in A000043.
a(n) = 3 for n in {1,4,10,12,24,27,39,...}.
a(n) = 5 for n in {26,76,132,205,238,...}.
a(n) = 9 for n in {100,200,...}.
a(n) = 15 for n in {15,33,65,...}.
a(21) = 18. a(22) = 13. a(41) = 6. a(72) = 11. a(173) = 8.
a(20) > 2100 [From Max Alekseyev (maxale(AT)gmail.com), Jul 07 2009]
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LINKS
| Eric Weisstein, Link to a section of The World of Mathematics. Harmonic Number.
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CROSSREFS
| Cf. A058313, A119682, A120296, A001008, A000043.
Sequence in context: A127807 A122028 A049234 * A075392 A069901 A115039
Adjacent sequences: A125501 A125502 A125503 * A125505 A125506 A125507
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KEYWORD
| hard,more,nonn
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AUTHOR
| Alexander Adamchuk (alex(AT)kolmogorov.com), Dec 28 2006, Jan 31 2007
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EXTENSIONS
| More terms from Max Alekseyev (maxale(AT)gmail.com), Jul 07 2009
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