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

1, 2, 6, 126, 8598

Offset: 1

Author

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

Keywords

• nonn
• more

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

Examples

			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.
		

Links

• Dario Alpern, Integer factorization calculator.

Crossrefs

Cf. A031973.

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

Formula

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

Extensions

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

Edited by Thomas Ordowski, Sep 02 2021