

A088275


Numbers n such that 10^n + 9 is prime.


24



1, 2, 3, 4, 9, 18, 22, 45, 49, 56, 69, 146, 202, 272, 2730, 2841, 4562, 31810, 43186, 48109, 92691
(list;
graph;
refs;
listen;
history;
text;
internal format)



OFFSET

1,2


COMMENTS

No others less than 9000.  Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
No others less than 39254.  Dirk Augustin, Oct 24 2006
2730, 2841 and 4562 all give primes.  Joao da Silva (zxawyh66(AT)yahoo.com), Sep 30 2005
Verified existing terms. No other terms less than 40001.  Robert Price, Aug 14 2010
No other terms <= 100,000.  Robert Price, Mar 03 2011
a(22) > 2*10^5.  Robert Price, Oct 11 2015


LINKS

Table of n, a(n) for n=1..21.
Makoto Kamada, Prime numbers of the form 100...009.
Sabin Tabirca and Kieran Reynolds, Lacunary Prime Numbers.


FORMULA

a(n) = A102008(n) + 1.


EXAMPLE

4 is a member since 10^4 + 9 = 10009 is a prime.


MATHEMATICA

Do[ If[ PrimeQ[ 10^n + 9], Print[n]], {n, 0, 10000}] (* Robert G. Wilson v, Dec 16 2004 *)


PROG

(PARI) is(n)=isprime(10^n + 9) \\ Charles R Greathouse IV, Apr 29 2015


CROSSREFS

Cf. A049054, A088274, A102008.
Sequence in context: A281882 A325436 A145027 * A274836 A322783 A014281
Adjacent sequences: A088272 A088273 A088274 * A088276 A088277 A088278


KEYWORD

nonn


AUTHOR

Amarnath Murthy, Sep 28 2003


EXTENSIONS

a(8)a(16) from Ray Chandler, Oct 10 2003
a(17) from Julien Peter Benney (jpbenney(AT)ftml.net), Jan 15 2005
a(18) (a PRP) found by Dirk Augustin, Oct 16 2006
Two more terms (probable primes), found with WinPFGW. No others less than 60400.  Jason Earls, Dec 22 2007
a(21)=92691 from Robert Price, Mar 03 2011


STATUS

approved



