A292188 - OEIS

A292188

Composite numbers m such that all prime divisors p > m of 2^m - 1 are of the form p = 2*k*m + 1.

8, 9, 15, 21, 24, 32, 39, 51, 57, 64, 65, 75, 85, 93, 111, 115, 121, 133, 183, 201, 217, 265, 267, 279, 303, 305, 309, 321, 341, 381, 415, 417, 427, 445, 671, 745, 771, 807, 813, 843, 879, 889, 1041, 1047, 1059, 1119, 1137, 1203

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OFFSET

1,1

COMMENTS

There are no terms of the forms q-1 and 2q with q prime.

Are there infinitely many the terms m = 3q with q prime?

LINKS

Table of n, a(n) for n=1..48.

EXAMPLE

For 2^15 - 1 = 7*31*151, 30/15 = 2 and 150/15 = 10, so 15 is a term.

For 2^16 - 1 = 3*5*17*257, 16/16 = 1 is odd, so 16 is not a term.

CROSSREFS

Cf. A000040, A000225, A060443.

Sequence in context: A050688 A134334 A351048 * A301659 A265221 A286476

Adjacent sequences: A292185 A292186 A292187 * A292189 A292190 A292191

KEYWORD

nonn

AUTHOR

Thomas Ordowski, Sep 11 2017

EXTENSIONS

a(13)-a(48) from Max Alekseyev, Sep 11 2017

STATUS

approved