OFFSET
1,3
COMMENTS
a(22) > 10^5. - Robert Price, Nov 16 2014
a(23) > 2*10^5. - Robert Price, Jul 11 2015
REFERENCES
Mark A. Herkommer, Number Theory, A Programmer's Guide, McGraw-Hill, New York, 1999, page 51.
LINKS
Makoto Kamada, Prime numbers of the form 200...003.
Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.
FORMULA
a(n) = A101951(n-1) + 1.
EXAMPLE
2+3 is prime, so are 23, 2003, 200003, 2000003, 20000003,2000000000003, etc. which are all of the form 2*10^n +3.
MATHEMATICA
Do[ If[ PrimeQ[2*10^n + 3], Print[n]], {n, 0, 10000}]
Select[Range[0, 1000], PrimeQ[(2 10^# + 3)] &] (* Vincenzo Librandi, Nov 17 2014 *)
PROG
(Magma) [n: n in [0..500] | IsPrime(2*10^n+3)]; // Vincenzo Librandi, Nov 17 2014
(PARI) is(n)=isprime(2*10^n+3) \\ Charles R Greathouse IV, Feb 17 2017
CROSSREFS
KEYWORD
more,nonn
AUTHOR
Robert G. Wilson v, Mar 26 2003
EXTENSIONS
More terms from Robert G. Wilson v, Jan 18 2005
a(20)-a(21) from Kamada data by Robert Price, Dec 09 2010
a(22) from Robert Price, Jul 11 2015
STATUS
approved