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%I #14 Sep 08 2022 08:45:28
%S 1,7,51,611,19839,603331,32981935,1469991559,108336139407,
%T 17389027481287,1334783150250945,222909199163881075,
%U 31099653342061054699,2994181661163361882651,387134597481460117602345,92092112661138292186297999,26679920606217066273305101055
%N a(n) = Sum_{i=1..n} (prime(i)^n - 1)/(prime(i) - 1).
%H Vincenzo Librandi, <a href="/A124271/b124271.txt">Table of n, a(n) for n = 1..200</a>
%t Table[Sum[(Prime[i]^n-1)/(Prime[i]-1),{i,1,n}],{n,1,20}]
%o (PARI) a(n) = sum(i=1, n, (prime(i)^n - 1)/(prime(i) - 1)) \\ _Jianing Song_, Oct 20 2018
%o (Magma) [&+[(NthPrime(k)^n - 1) div (NthPrime(k) - 1): k in [1..n]]: n in [1..20]]; // _Vincenzo Librandi_, Oct 21 2018
%Y Cf. A124272 (prime terms of this sequence), A124273 (primes p that divide a(p)), A124274 (nonprimes n that divide a(n)).
%Y Similar sequence: A123855. See also A123856.
%K nonn
%O 1,2
%A _Alexander Adamchuk_, Oct 23 2006
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