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%I #15 Feb 06 2018 09:24:04
%S 11,131,2,5,10301,16361,10281118201,35605550653,7159123219517,
%T 17401539893510471,3205657651567565023
%N Smallest palindromic prime that generates a palindromic prime pyramid of height n.
%C Start with a palindromic prime p; look for smallest palindromic prime that has previous term as a centered substring and has 2 more digits (i.e., one more digit at each end); repeat until no such palindromic prime can be found; then height(p) = number of rows in pyramid. Each row of pyramid must be the smallest prime that can be used. Then a(n) = smallest value of p that generates a pyramid of height n.
%H G. L. Honaker, Jr. and Chris K. Caldwell, <a href="http://www.utm.edu/staff/caldwell/preprints/jrm_prime_pyramids.pdf">Palindromic prime pyramids</a>
%H Ivars Peterson's MathTrek, <a href="https://www.sciencenews.org/article/primes-palindromes-and-pyramids">Primes, Palindromes, and Pyramids</a>
%H Chai Wah Wu, <a href="http://arxiv.org/abs/1503.08883">On a conjecture regarding primality of numbers constructed from prepending and appending identical digits</a>, arXiv:1503.08883 [math.NT], 2015.
%e a(1) = 11.
%e a(4) = 5:
%e 5
%e 151
%e 31513
%e 3315133, stop;
%e height(5)=4.
%e a(6)=16362:
%e 16361
%e 1163611
%e 311636113
%e 33116361133
%e 3331163611333
%e 333311636113333, stop;
%e height(16361)=6.
%Y Cf. A034276, A052205, A053600.
%K nonn,base,more
%O 1,1
%A _Felice Russo_, Jan 25 2000
%E Added a(10)-a(11) and corrected a(4) - _Chai Wah Wu_, Apr 09 2015
%E Entry revised by _N. J. A. Sloane_, Apr 13 2015
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