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A186521 Numbers n>0 such that (7*10^(n+2)+666)*10^n+7 is prime. 2
1, 3, 6, 7, 49, 578, 793, 1322, 1392, 2392, 3066, 13479 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

COMMENTS

Or, indices of primes in A046720. Rudolf Ondrejka calls these "beastly palindromic primes".

Some of the larger entries may only correspond to probable primes.

LINKS

Table of n, a(n) for n=1..12.

Chris Caldwell, The Prime Glossary, Beastly prime

G. L. Honaker, Jr. and Chris Caldwell, Prime Curios! 76667

R. Ondrejka, The Top Ten: a Catalogue of Primal Configurations

MATHEMATICA

Select[Range[10^3], PrimeQ[(7*10^(# + 2) + 666)*10^# + 7] &] (* Arkadiusz Wesolowski, Sep 08 2011 *)

CROSSREFS

Cf. A046720, A186086.

Sequence in context: A287502 A287538 A233209 * A067697 A137128 A256372

Adjacent sequences:  A186518 A186519 A186520 * A186522 A186523 A186524

KEYWORD

more,nonn,base

AUTHOR

Arkadiusz Wesolowski, Feb 23 2011

EXTENSIONS

Added a(12)=13479, Arkadiusz Wesolowski, Mar 16 2011.

STATUS

approved

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Last modified January 29 05:09 EST 2022. Contains 350672 sequences. (Running on oeis4.)