A216551 Numbers n such that (2^n+1)/3 is prime, but cannot be written in the form a^2 + 3*b^2.

5, 11, 17, 23, 101, 167, 191, 347, 701, 1709, 3539, 5807, 10691, 11279, 42737, 83339, 95369, 117239, 127031, 267017, 269987, 374321, 4031399

Offset

1,1

Comments

The exponent is congruent to 2 mod 3.

Links

Table of n, a(n) for n=1..23.

Samuel S. Wagstaff, Jr. The Cunningham Project

Crossrefs

Cf. A000978.

Sequence in context: A268640 A360542 A214912 * A314255 A369274 A246296

Adjacent sequences: A216548 A216549 A216550 * A216552 A216553 A216554

Keyword

nonn

Author

V. Raman, Sep 08 2012

Status

approved