OFFSET
1,3
COMMENTS
761 and 9205 only probably prime. No others less than 10000.
a(12) > 2*10^5. - Robert Price, Jun 06 2015
LINKS
Makoto Kamada, Prime numbers of the form 200...009.
Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.
FORMULA
a(n) = A101952(n-1) + 1 for n>1.
EXAMPLE
n = 1, 5 are members since 29 and 200009 are primes.
MATHEMATICA
Do[ If[ PrimeQ[2*10^n + 9], Print[n]], {n, 0, 10000}]
PROG
(PARI) is(n)=ispseudoprime(2*10^n+9) \\ Charles R Greathouse IV, Jun 12 2017
CROSSREFS
KEYWORD
hard,nonn
AUTHOR
Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
EXTENSIONS
a(8)-a(9) from Kamada link by Herman Jamke (hermanjamke(AT)fastmail.fm), Jan 02 2008
a(10)-a(11) from Kamada data by Robert Price, Dec 13 2010
Prepended a(1)=0 by Robert Price, Jun 06 2015
STATUS
approved