1,1

2^2-1=3 is prime; (3^3-1)/2=13 is prime; (5^13-1)/4=305175781 is prime; the next term is too gigantic to be computed simply.

Table of n, a(n) for n=1..3.

a(p)=((p^a(p-1))-1)/(p-1); a(p)=111...111 in base p with a(p-1) 1's; p runs though the primes.

Sequence in context: A317481 A271393 A087345 * A174211 A264611 A157323

Adjacent sequences: A048753 A048754 A048755 * A048757 A048758 A048759

nonn,bref

Xavier Labouze (Xavier.Labouze(AT)cep.u-psud.fr)

approved