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Search: id:A129764
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| A129764 |
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Numerator of the sum of all elements of n X n X n cubic array M[i,j,k] = 1/(i+j+k-2). |
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1
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| 1, 15, 1133, 1177, 129149, 349673, 57087959, 345322023, 14272692271, 40165727117, 217549734472087, 14553241481573, 18901300532988407, 40603763694792631, 9565202506169243753, 63888449105310899
(list; graph; listen)
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OFFSET
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1,2
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COMMENT
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a(n) is a 3-d analog of Wolstenholme Numbers (A001008) that are the numerators of Harmonic Numbers H(n) = Sum[ 1/i, {i,1,n} ]. n X n X n cubic array M[i,j,k] = 1/(i+j+k-2) is a 3-d analog of n X n Hilbert Matrix with elements M[i,j] = 1/(i+j-1). p divides a((p+1)/3) for prime p = {5,11,17,23,29,41,47,53,59,71,83,89,...} = A007528 Primes of form 6n-1. Sum[ Sum[ Sum[ (i+j+k-2), {i,1,n} ], {j,1,n} ], {k,1,n} ] = 1/2*n^3*(3n-1).
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LINKS
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Eric Weisstein, The World of Mathematics: Hilbert Matrix.
Eric Weisstein, The World of Mathematics: Harmonic Number.
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FORMULA
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a(n) = Numerator[ Sum[ Sum[ Sum[ 1/(i+j+k-2), {i,1,n} ], {j,1,n} ], {k,1,n} ] ].
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MATHEMATICA
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Table[ Numerator[ Sum[ Sum[ Sum[ 1/(i+j+k-2), {i, 1, n} ], {j, 1, n} ], {k, 1, n} ] ], {n, 1, 30} ]
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CROSSREFS
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Cf. A001008 = Wolstenholme numbers: numerator of harmonic number H(n)=Sum_{i=1..n} 1/i. Cf. A082687, A117731, A007528.
Sequence in context: A082158 A064625 A131313 this_sequence A027552 A098210 A090213
Adjacent sequences: A129761 A129762 A129763 this_sequence A129765 A129766 A129767
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KEYWORD
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nonn
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AUTHOR
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Alexander Adamchuk (alex(AT)kolmogorov.com), May 15 2007
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