A101753 Numbers m such that Sum_{k=0..m} m^k is prime.

1, 2, 6, 126, 8598

Offset

1,2

Comments

Value of sum for m = 126 has been checked to be probably prime with the isprime functions of PARI and Maple V. Also checked with ECM - see link.

Note that m+1 must be prime and hence a(n) = A088856(n) - 1. Another way to compute the number is (m^(m + 1) - 1)/(m - 1). - T. D. Noe, Dec 15 2004

Value of sum for m = 126 has been certified prime with Primo. - Ryan Propper, Jul 11 2005

Links

Table of n, a(n) for n=1..5.

Dario Alpern, Integer factorization calculator.

Formula

a(n) = A088856(n) - 1.

Example

The number 6 is in this sequence because 6^0 + 6^1 + 6^2 + 6^3 + 6^4 + 6^5 + 6^6 = (6^7 - 1)/5 = 55987 is prime.

Crossrefs

Cf. A031973.

Cf. A088856 (primes p such that cyclotomic(p,p-1) is prime).

Sequence in context: A164955 A060001 A181316 * A288185 A359961 A274695

Adjacent sequences: A101750 A101751 A101752 * A101754 A101755 A101756

Keyword

nonn,more

Author

Mark Hudson (mrmarkhudson(AT)hotmail.com), Dec 15 2004

Extensions

One more term from T. D. Noe, Dec 15 2004

Edited by Thomas Ordowski, Sep 02 2021

Status

approved