OFFSET
1,2
COMMENTS
a(13) > 2*10^5. - Robert Price, Jan 19 2015
REFERENCES
R. K. Guy, Unsolved Problems in Theory of Numbers, Section A3.
LINKS
H. C. Williams, The primality of certain integers of the form 2Ar^n - 1, Acta Arith. 39 (1981), 7-17.
MATHEMATICA
Do[ If[ PrimeQ[10*11^n - 1], Print[n]], {n, 1, 2000}]
PROG
(PARI) is(n)=isprime(10*11^n-1) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
KEYWORD
nonn,hard
AUTHOR
EXTENSIONS
One more term from Robert G. Wilson v, Jan 16 2003
a(10)-a(12) from Robert Price, Jan 19 2015
STATUS
approved