OFFSET
1,1
COMMENTS
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.
LINKS
Prime Pages, Lehmer number
EXAMPLE
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.
CROSSREFS
KEYWORD
nonn
AUTHOR
David Broadhurst, Mar 28 2009
STATUS
approved