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Numbers k such that the smoothly undulating palindromic number (97*10^k - 79)/99 is a prime.
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%I #19 Mar 24 2021 18:37:40

%S 9,27,45,237

%N Numbers k such that the smoothly undulating palindromic number (97*10^k - 79)/99 is a prime.

%C Prime versus probable prime status and proofs are given in the author's table.

%C No further terms < 100000. - _Ray Chandler_, Aug 17 2011

%H Patrick De Geest, <a href="http://www.worldofnumbers.com/undulat.htm#supp979">SUPP Reference Table - 979</a>

%H <a href="/index/Pri#pri_supp">Index entries for sequences related to smoothly undulating palindromic primes</a>

%e k=27 -> (97*10^27 - 79)/99 = 979797979797979797979797979.

%t Select[Range[1,239,2],PrimeQ[FromDigits[PadRight[{},#,{9,7}]]]&] (* _Harvey P. Dale_, Mar 24 2021 *)

%Y Cf. A062209-A062232, A059758, A032758.

%K nonn,base,more

%O 1,1

%A _Patrick De Geest_ and Hans Rosenthal (Hans.Rosenthal(AT)t-online.de), Jun 15 2001

%E Edited by _Ray Chandler_, Aug 17 2011