1,1

Equivalently, smallest prime of the form (p^(k+1)-1)/(p-1), where p is the n-th prime.

For p prime, the sum of divisors of p^k is Sum_{j=0..k} p^j, so a(n) is the smallest prime of the form sigma(prime(n)^k) where sigma is the sum of divisors function A000203.

For the corresponding values of k, see A279069.

a(15) = 1 + 47 + 47^2 + ... + 47^126 = 4.93935...*10^210.

a(57) > 10^10000.

Table of n, a(n) for n=1..14.

Cf. A000203, A279069.

Sequence in context: A073337 A128067 A052493 * A247216 A301926 A211800

Adjacent sequences: A279065 A279066 A279067 * A279069 A279070 A279071

nonn

Jon E. Schoenfield, Dec 22 2016; edited Dec 23 2016

approved