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Search: id:A128648
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| A128648 |
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Denominator of Sum[ (-1)^(k+1)*1/(Prime[k]-1), {k,1,n} ]. |
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+0
4
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| 1, 2, 4, 12, 60, 5, 80, 720, 7920, 55440, 55440, 6160, 6160, 18480, 425040, 5525520, 160240080, 160240080, 53413360, 53413360, 480720240, 480720240, 19709529840, 19709529840, 39419059680, 197095298400, 3350620072800, 177582863858400
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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A128647(n) = {1,1,3,7,41,3,53,437,5167,34189,36037,3833,3987,11521,...} = Numerator of Sum[ (-1)^(k+1)*1/(Prime[k]-1), {k,1,n} ]. A128646(n) = {1,2,4,12,60,10,80,720,7920,55440,55440,18480,18480,18480,425040,...} = Denominator of Sum[ 1/(Prime[k]-1), {k,1,n} ]. Numbers n such that a(n) equals A128646(n) are listed in A128649(n) = {1,2,3,4,5,7,8,9,10,11,14,15,16,17,21,22,23,24,25,26,27,28,29,30,31,32,33,34,35,65,66,71,...}.
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LINKS
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Eric Weisstein, Link to a section of The World of Mathematics. Prime Sums.
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FORMULA
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a(n) = Denominator[ Sum[ (-1)^(k+1)*1/(Prime[k]-1), {k,1,n} ] ].
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MATHEMATICA
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Table[Denominator[Sum[(-1)^(k+1)*1/(Prime[k]-1), {k, 1, n}]], {n, 1, 36}]
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CROSSREFS
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Cf. A128647 = Numerator of Sum[ (-1)^(k+1)*1/(Prime[k]-1), {k, 1, n} ]. Cf. A128646 = Denominator of Sum[ 1/(Prime[k]-1), {k, 1, n} ]. Cf. A128649, A120271, A119686, A006093, A000040.
Adjacent sequences: A128645 A128646 A128647 this_sequence A128649 A128650 A128651
Sequence in context: A020106 A099928 A000568 this_sequence A128646 A058254 A076244
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KEYWORD
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frac,nonn
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AUTHOR
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Alexander Adamchuk (alex(AT)kolmogorov.com), Mar 18 2007
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