OFFSET
1,2
COMMENTS
Or, indices of primes in the sequence 16661, 1066601, 100666001, 10006660001,... Ondrejka calls these "beastly palindromic primes".
In popular culture: the number generated by a(2), 1000000000000066600000000000001, also known as Belphegor's Prime, was used as a plot device in Episode "Just a Regular Irregular" of the "Elementary" TV series (first aired Nov/13/2014). - Serge Batalov, Nov 15 2014
LINKS
C. Caldwell, H. Dubner (Eds): The top ten prime numbers: from the unpublished collections of R. Ondrejka (May 2001), p. 32
Internet Movie Database, Elementary: Season 3, Episode 3: Just a Regular Irregular
Clifford A. Pickover, Belphegor's Prime: 1000000000000066600000000000001
Eric Weisstein's World of Mathematics, Belphegor Prime
Eric Weisstein's World of Mathematics, Integer Sequence Primes
Wikipedia, Belphegor's prime
FORMULA
a(n) = A232448(n) + 1.
MAPLE
A156166:=n->`if`(isprime((10^(n+2)+666)*10^n+1), n, NULL): seq(A156166(n), n=1..10^3); # Wesley Ivan Hurt, Nov 16 2014
MATHEMATICA
Select[Range[10^3], PrimeQ[(10^(# + 2) + 666)*10^# + 1] &] (* Arkadiusz Wesolowski, Sep 08 2011 *)
PROG
(PARI) for( n=1, 9999, ispseudoprime((10^(n+2)+666)*10^n+1) & print1(n", "))
(Magma) [n: n in [1..500] | IsPrime((10^(n+2)+666)*10^n+1)]; // Vincenzo Librandi, Nov 15 2014
CROSSREFS
KEYWORD
more,nonn,base,changed
AUTHOR
M. F. Hasler, Feb 10 2009
EXTENSIONS
a(8) = 28292 (discovered on Jan 05 2004, by Daniel Heuer), Arkadiusz Wesolowski, Mar 16 2011
a(9) = 181299 from Serge Batalov, Nov 15 2014
STATUS
approved