A124274 Nonprime numbers n that divide A124271(n) = Sum_{i=1..n} (prime(i)^n - 1) / (prime(i) - 1).

1, 9, 15, 121

Offset

1,2

Comments

The next term if it exists is greater than 1000.

Note that a(1) = 1, a(2) = 3^2 and a(4) = 11^2 are perfect squares.

Links

Table of n, a(n) for n=1..4.

Example

9 is a term because 9 divides A124271(9) = 108336139407.

Crossrefs

Cf. A124271, A124273 (primes p that divide A124271(p)).

Sequence in context: A136354 A177184 A098146 * A075134 A316744 A158789

Adjacent sequences: A124271 A124272 A124273 * A124275 A124276 A124277

Keyword

bref,hard,more,nonn

Author

Alexander Adamchuk, Oct 23 2006

Status

approved