

A156166


Numbers k > 0 such that (10^(k+2) + 666)*10^k + 1 is prime.


4




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


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FORMULA



MAPLE



MATHEMATICA



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

Cf. A082700 and search results for 16661.


KEYWORD

more,nonn,base


AUTHOR



EXTENSIONS



STATUS

approved



