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A124271
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a(n) = Sum_{i=1..n} (prime(i)^n - 1)/(prime(i) - 1).
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5
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1, 7, 51, 611, 19839, 603331, 32981935, 1469991559, 108336139407, 17389027481287, 1334783150250945, 222909199163881075, 31099653342061054699, 2994181661163361882651, 387134597481460117602345, 92092112661138292186297999, 26679920606217066273305101055
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OFFSET
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1,2
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LINKS
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MATHEMATICA
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Table[Sum[(Prime[i]^n-1)/(Prime[i]-1), {i, 1, n}], {n, 1, 20}]
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PROG
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(PARI) a(n) = sum(i=1, n, (prime(i)^n - 1)/(prime(i) - 1)) \\ Jianing Song, Oct 20 2018
(Magma) [&+[(NthPrime(k)^n - 1) div (NthPrime(k) - 1): k in [1..n]]: n in [1..20]]; // Vincenzo Librandi, Oct 21 2018
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CROSSREFS
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Cf. A124272 (prime terms of this sequence), A124273 (primes p that divide a(p)), A124274 (nonprimes n that divide a(n)).
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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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