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A178188
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a(n) = Sum_{k=1..n} 5^((k^2+3k)/2).
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1
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25, 3150, 1956275, 6105471900, 95373537112525, 7450675970460940650, 2910390496349340822268775, 5684344796471297836309816409400, 55511156915602623492479419714357425025
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OFFSET
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1,1
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COMMENTS
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Series of the kind m^((k^2+3k)/2) from k=1 to n was studied by Bernoulli and Euler.
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LINKS
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MATHEMATICA
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aa = {}; m = 5; sum = 0; Do[sum = sum + m^((n + 3) n/2); AppendTo[aa, sum], {n, 1, 20}]; aa (*Artur Jasinski*)
Table[Sum[5^((k^2+3k)/2), {k, n}], {n, 10}] (* Harvey P. Dale, Jan 17 2015 *)
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PROG
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(PARI) a(n) = sum(k=1, n, 5^((k^2+3*k)/2)); \\ Michel Marcus, Sep 09 2013
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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