1,2

Value of sum for n=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 n+1 must be prime, and hence a(k)=A088856(k)-1. Another way to compute the number is (n^(n+1)-1)/(n-1). - T. D. Noe (noe(AT)sspectra.com), Dec 15 2004

Value of sum for n=126 has been certified prime with Primo. - Ryan Propper (rpropper(AT)stanford.edu), Jul 11 2005

www.alpertron.com, ECM.HTM

6 is in the sequence because 6^0 + 6^1 + 6^2 + 6^3 + 6^4 + 6^5 + 6^6 = 55987 is prime.

Cf. A031973.

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

Sequence in context: A058251 A039716 A060001 this_sequence A090907 A047937 A027731

Adjacent sequences: A101750 A101751 A101752 this_sequence A101754 A101755 A101756

more,nonn

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

One more term from T. D. Noe (noe(AT)sspectra.com), Dec 15 2004