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 A046720 Subsequence of beastly primes (A186086) that are palindromes that begin and end with 7. 6
 76667, 700666007, 700000666000007, 70000006660000007 (list; graph; refs; listen; history; text; internal format)
 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 EXTENSIONS Definition revised by N. J. A. Sloane, Feb 14 2011 STATUS approved

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Last modified August 6 16:05 EDT 2020. Contains 336255 sequences. (Running on oeis4.)