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Search: id:A143345
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| A143345 |
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a(n) = number of terms in successive rows of triangle A080092, = number of prime factors in denominators of Bernoulli numbers B1, B2, B4, B6,... |
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+0
2
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OFFSET
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1,2
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COMMENT
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B12 = -691/2730, derived from the 5 primes, = (1 - 1/2, - 1/3, - 1/5 - 1/7 - 1/13) as shown in A143343 and A080092.
Essentially the same as A046886. [From R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Sep 23 2009]
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FORMULA
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Number of terms in successive rows of triangle A080092, = number of prime factors in denominators of Bernoulli numbers B1, B2, B4, B6,...
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EXAMPLE
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The first 5 in the sequence pertains to B12 = -691/2730 since there are 5 prime factors of 2730: (2*3*5*7*13) as shown in A143343, A080092 and A138243.
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CROSSREFS
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Cf. A143343, A080092, A138243, A027642, A002445.
Sequence in context: A029109 A029090 A029089 this_sequence A046886 A155047 A029088
Adjacent sequences: A143342 A143343 A143344 this_sequence A143346 A143347 A143348
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KEYWORD
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nonn
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AUTHOR
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Gary W. Adamson & Mats O. Granvik (qntmpkt(AT)yahoo.com), Aug 09 2008
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