Cuban primes: Difference between revisions

<lang Common Lisplisp>;;; Show the first 200 and the 100,000th cuban prime.

(cond ((< n 4) t)

((evenp n) nil)

((zerop (mod n 3)) nil)

(t (loop for i from 5 upto (isqrt n) by 6

when (or

(zerop (mod n i))

(zerop (mod n (+ i 2))))

return nil

finally (return t)))))

(loop for i from 1

for j from 2

for cube-diff = (- (cube j) (cube i))

collect cube-diff into cuban-primes

and count i into counter

when (equal= counter n)

return cuban-primes))