A260867 Least k > 1 that divides A260868(n) + 2^k - 2.

35, 161, 55, 35, 115, 35, 115, 35, 77, 209, 473, 253, 55, 77, 35, 235, 247, 55, 35, 35, 899, 119, 1003, 415, 143, 35, 335, 95, 299, 497, 203, 575, 35, 247, 323, 95, 77, 437, 901, 35, 55, 473, 35, 1457, 77, 55, 517, 35, 235, 493, 161, 535, 209, 115, 95, 1067, 689, 323, 35, 1199, 1313, 355, 77, 815, 635, 869, 235, 119, 551, 55, 115

Offset

1,1

Comments

For all numbers N not listed in A260868, the least k > 1 that divides N + 2^k - 2 is equal to the least prime factor of N.

It appears that the range of this sequence is A267999. For example, 155 occurs first somewhat late for N = 2729. - Corrected by Thomas Ordowski, Oct 27 2018

Links

Table of n, a(n) for n=1..71.

Prog

(PARI) my(aa(n)=for(k=2, 9e9, Mod(2, k)^k+n-2||return(k))); for(n=2, 1e5, aa(n)==factor(n)[1, 1]||print1(aa(n)", "))

Crossrefs

Sequence in context: A005339 A045614 A154074 * A015219 A195545 A270860

Adjacent sequences: A260864 A260865 A260866 * A260868 A260869 A260870

Keyword

nonn

Author

M. F. Hasler, Aug 11 2015

Status

approved