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A139208
Numbers 2*k+1 for which numbers A006694(k) are record values for A006694.
0
1, 3, 7, 15, 21, 31, 45, 63, 93, 105, 127, 189, 217, 255, 315, 341, 455, 511, 819, 1023, 1365, 2047, 3591, 3855, 4095, 5461, 8191, 12483, 13107, 16383, 21845, 29127, 32767, 53261, 55831, 60787, 65535, 87381, 131071, 178481, 182361, 209715, 258111, 262143, 349525, 430185, 479349, 524287
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
Sequence in context: A121712 A175544 A373941 * A324727 A320026 A146435
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