A038844 n for which 6n+1 | 2^n-1.

5, 21, 37, 72, 73, 76, 100, 121, 153, 221, 233, 237, 245, 276, 288, 292, 296, 300, 305, 333, 336, 341, 348, 352, 357, 380, 381, 397, 445, 448, 461, 465, 472, 492, 545, 557, 565, 576, 577, 601, 605, 637, 648, 657, 676, 688, 692, 696, 737, 752, 753, 761, 776

Offset

1,1

Comments

Apart from 5, all terms are in A045762, numbers such that 2^n-1 is not prime. - Michel Marcus, Nov 12 2014

Links

Harvey P. Dale, Table of n, a(n) for n = 1..1000

Example

For n=5, 2^5-1=31 is divisible by 6*5+1=31.

Mathematica

Select[Range[800], PowerMod[2, #, 6#+1]==1&] (* Harvey P. Dale, Oct 24 2017 *)

Prog

(PARI) select( {is_A038844(n)=Mod(2, n*6+1)^n==1}, [1..999]) \\ M. F. Hasler, Aug 17 2021

Crossrefs

Cf. A045762, A188130 (subsequence of primes).

Sequence in context: A170876 A373193 A341198 * A303521 A365767 A372518

Adjacent sequences: A038841 A038842 A038843 * A038845 A038846 A038847

Keyword

nonn

Author

Bill Gosper

Extensions

More terms from Michel Marcus, Nov 12 2014

Status

approved