OFFSET
0,2
EXAMPLE
a(n)=777 -> nextprime(a(n)) is 787 so '777787' is prime (=step 1); a(n2)=777787 -> nextprime(a(n2)) is 777817 so '777787777817' is prime (=step 2).
CROSSREFS
KEYWORD
nonn,base
AUTHOR
Patrick De Geest, Oct 15 1998
STATUS
approved