1,1

The Lehmer number (x^n-1/x^n)/(x-1/x), with x = sqrt(3) + sqrt(2), may be prime only if the index n is prime. For the listed indices up to n = 1997 the Lehmer number is prime; thereafter it is a probable prime.

Table of n, a(n) for n=1..20.

Prime Pages, Lehmer number

a(3) = 37 since ((sqrt(3)+sqrt(2))^37-(sqrt(3)-sqrt(2))^37)/(2*sqrt(2)) = 926569189346784589 is the third prime in this Lehmer sequence.

Sequence in context: A145640 A222496 A086158 * A337858 A337859 A184314

Adjacent sequences: A158875 A158876 A158877 * A158879 A158880 A158881

nonn

David Broadhurst, Mar 28 2009

approved