A236769 Numbers n such that lpf(2^n -1) < lpf(2^lpf(n) -1).

55, 77, 161, 169, 221, 275, 299, 323, 377, 385, 391, 437, 481, 493, 539, 551, 559, 605, 611, 629, 689, 697, 703, 715, 731, 779, 793, 799, 817, 847, 893, 901, 923, 935, 949, 1001, 1007, 1027, 1045, 1073, 1079, 1121, 1127, 1147, 1159, 1241, 1265, 1271, 1273, 1309

Offset: 1

Author

Thomas Ordowski, Jan 31 2014

Keywords

• nonn

Comments

The numbers n for which A049479(n) < A049479(lpf(n)), where lpf(n) = A020639(n). All other n satisfy the equality (in particular all primes).

All terms are odd and composite. - Chai Wah Wu, Oct 04 2019

Links

• Chai Wah Wu, Table of n, a(n) for n = 1..111

Crossrefs

Cf. A049479 (a question in the third comment).

Programs

PARI

lpf(n) = vecmin(factor(n)[, 1]);
lista() = {my(vlpfmp = readvec("A049479.log")); for (i=2, #vlpfmp, if (vlpfmp[i] < vlpfmp[lpf(i)], print1(i, ", ")););} \\ Michel Marcus, Jan 31 2014

Extensions

More terms from Michel Marcus, Jan 31 2014

More terms from Chai Wah Wu, Oct 04 2019