The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A297362 Numbers n such that (2^ord(2, n) - 1)/n is prime, where ord(2, n) is the multiplicative order of 2 (mod n). 0
 5, 9, 21, 23, 33, 47, 51, 73, 85, 89, 93, 129, 167, 217, 223, 263, 315, 341, 381, 585, 819, 1057, 1365, 3591, 3855, 4681, 4871, 5461, 6141, 6223, 6719, 7487, 8193, 11447, 13107, 13367, 13797, 14329, 16513, 18631, 21845, 24573, 25575, 26431, 33825, 37449 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS The corresponding primes are 3, 7, 3, 89, 31, 178481, 5, 7, 3, 23, 11, ... LINKS EXAMPLE 5 is in the sequence since ord(2, 5) = 4 and (2^4 - 1)/5 = 3 is prime. MATHEMATICA aQ[n_] := PrimeQ[(2^MultiplicativeOrder[2, n] - 1)/n]; Select[Range[10000], aQ] CROSSREFS Cf. A002326, A165781. Sequence in context: A273150 A273388 A273449 * A175364 A244642 A211424 Adjacent sequences:  A297359 A297360 A297361 * A297363 A297364 A297365 KEYWORD nonn AUTHOR Amiram Eldar, Dec 29 2017 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified April 22 07:26 EDT 2021. Contains 343163 sequences. (Running on oeis4.)