OFFSET
1,2
COMMENTS
Question. Is it true that all primes in this sequence are Mersenne primes?
178481 is a prime term, but is not a Mersenne prime. - Michel Marcus, Dec 18 2018
PROG
(PARI) a006694(n)=sumdiv(2*n+1, d, eulerphi(d)/znorder(Mod(2, d))) - 1;
lista(nn) = {my(m = -1, newm); for(n=0, nn, newm = a006694(n); if (newm > m, m = newm; print1(2*n+1, ", ")); ); } \\ Michel Marcus, Dec 18 2018
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladimir Shevelev, Jun 06 2008
EXTENSIONS
Offset 1, missing term 819 and more terms from Michel Marcus, Dec 18 2018
STATUS
approved