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Search: id:A143128
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| A143128 |
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Sum {k=1..n} k*sigma(k). |
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+0
2
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| 1, 7, 19, 47, 77, 149, 205, 325, 442, 622, 754, 1090, 1272, 1608, 1968, 2464, 2770, 3472, 3852, 4692, 5364, 6156, 6708, 8148, 8923, 10015, 11095, 12663, 13533, 15693, 16685, 18701, 20285, 22121, 23801, 27077, 28483, 30763, 32947, 36547
(list; graph; listen)
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OFFSET
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1,2
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FORMULA
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Sum {k=1..n} k*sigma(k), where sigma(n) = A000203: (1, 3, 4, 7, 6, 12,...) and n*sigma(n) = A064987: (1, 6, 12, 28,...). Equals row sums of triangle A110662. - Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 12 2008
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EXAMPLE
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a(4) = 47 = (1 + 6 + 12 + 28) where A064987 = (1, 6, 12, 28, 30,...).
a(4) = 47 = sum of row 4 terms of triangle A110662 = (15 + 14 + 11 + 7).
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MAPLE
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with(numtheory): a:=proc(n) options operator, arrow: sum(k*sigma(k), k=1..n) end proc: seq(a(n), n=1..40); - Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 12 2008
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CROSSREFS
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Cf. A000203, A064987, A110662.
Sequence in context: A155399 A155415 A155273 this_sequence A139865 A146403 A000491
Adjacent sequences: A143125 A143126 A143127 this_sequence A143129 A143130 A143131
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KEYWORD
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nonn
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AUTHOR
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Gary W. Adamson (qntmpkt(AT)yahoo.com), Jul 26 2008
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EXTENSIONS
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Corrected and extended by Emeric Deutsch (deutsch(AT)duke.poly.edu), Aug 12 2008
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