OFFSET
1,1
PROG
(PARI) isok(n) = #select(x->isprime(x), vector(numdiv(n)^2-1, k, k+n)) == 1; \\ Michel Marcus, Jun 18 2017
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Benoit Cloitre, Apr 13 2002
STATUS
approved