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Search: id:A133298
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| A133298 |
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Sum[ i^(j+k), {i,1,n}, {j,1,n}, {k,1,n} ] + 1. |
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+0
1
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| 2, 41, 1727, 130917, 17245160, 3546873073, 1046002784253, 417182980579609, 215861313302976046, 140463714074395109081, 112191246261394235358555, 107867952671976721983260413, 122856922623618324408724634164
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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p divides a(p) for prime p>3. p^2 divides a(p) for prime p=7. Nonprime n dividing a(n) are {1,15}.
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FORMULA
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a(n) = Sum[ i^(j+k), {i,1,n}, {j,1,n}, {k,1,n} ] + 1. a(n) = Sum[ (i(i^n-1)/(i-1))^2, {i,2,n}] + n^2 + 1.
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MATHEMATICA
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Table[ Sum[ (i(i^n-1)/(i-1))^2, {i, 2, n} ] + n^2 + 1, {n, 1, 20} ]
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CROSSREFS
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Cf. A124405 = Sum[ i^j, {i, 1, n}, {j, 1, n} ] + 1. Cf. A062970, A086787.
Sequence in context: A112767 A058246 A129208 this_sequence A054742 A113634 A098634
Adjacent sequences: A133295 A133296 A133297 this_sequence A133299 A133300 A133301
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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), Oct 17 2007
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