OFFSET
1,2
COMMENTS
a(26) > 2*10^5. - Robert Price, Jul 14 2015
MATHEMATICA
Do[ f = 21^n - 2; If[ PrimeQ[ f ], Print[ {n, f} ] ], {n, 1, 1000} ]
CROSSREFS
KEYWORD
nonn,hard,more
AUTHOR
Alexander Adamchuk, Mar 14 2007
EXTENSIONS
2 more terms from Stefan Steinerberger, May 05 2007
a(17)-a(25) from Robert Price, Jul 14 2015
STATUS
approved