

A046720


Subsequence of beastly primes (A186086) that are palindromes that begin and end with 7.


6




OFFSET

1,1


COMMENTS

Next term is 7_{0}^48_666_{0}^48_7, containing 101 digits, and is too large to include here.
The number of digits in the terms is 2*A186521(n)+3: 5, 9, 15, 17, 101, 1159, 1589, 2647, 2787, 4787, 6135, 26961 (some correspond to probable primes)).  Jens Kruse Andersen, Jul 13 2014


LINKS

Jens Kruse Andersen, Table of n, a(n) for n = 1..7
R. Ondrejka, The Top Ten: a Catalogue of Primal Configurations
Tony Padilla and Brady Haran, The Most Evil Number, Numberphile video (2018)


FORMULA

a(n) = (7*10^(k+2)+666)*10^k+7, where k = A186521(n).  Jens Kruse Andersen, Jul 13 2014


MATHEMATICA

Select[Table[(7*10^(n + 2) + 666)*10^n + 7, {n, 7}], PrimeQ] (* Arkadiusz Wesolowski, Sep 08 2011 *)


CROSSREFS

Cf. A051003, A131645, A186086, A186521.
Sequence in context: A183744 A236709 A104327 * A258606 A152498 A237747
Adjacent sequences: A046717 A046718 A046719 * A046721 A046722 A046723


KEYWORD

base,nonn


AUTHOR

G. L. Honaker, Jr.


EXTENSIONS

Definition revised by N. J. A. Sloane, Feb 14 2011


STATUS

approved



