A124271 a(n) = Sum_{i=1..n} (prime(i)^n - 1)/(prime(i) - 1).

1, 7, 51, 611, 19839, 603331, 32981935, 1469991559, 108336139407, 17389027481287, 1334783150250945, 222909199163881075, 31099653342061054699, 2994181661163361882651, 387134597481460117602345, 92092112661138292186297999, 26679920606217066273305101055

Offset: 1

Author

Alexander Adamchuk, Oct 23 2006

Keywords

• nonn

Links

• Vincenzo Librandi, Table of n, a(n) for n = 1..200

Crossrefs

Cf. A124272 (prime terms of this sequence), A124273 (primes p that divide a(p)), A124274 (nonprimes n that divide a(n)).

Similar sequence: A123855. See also A123856.

Programs

Magma

[&+[(NthPrime(k)^n - 1) div (NthPrime(k) - 1): k in [1..n]]: n in [1..20]]; // Vincenzo Librandi, Oct 21 2018

Mathematica

Table[Sum[(Prime[i]^n-1)/(Prime[i]-1),{i,1,n}],{n,1,20}]

PARI

a(n) = sum(i=1, n, (prime(i)^n - 1)/(prime(i) - 1)) \\ Jianing Song, Oct 20 2018