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 A256957 Smallest palindromic prime that generates a palindromic prime pyramid of height n. 4
 11, 131, 2, 5, 10301, 16361, 10281118201, 35605550653, 7159123219517, 17401539893510471, 3205657651567565023 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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. LINKS G. L. Honaker, Jr. and Chris K. Caldwell, Palindromic prime pyramids Ivars Peterson's MathTrek, Primes, Palindromes, and Pyramids Chai Wah Wu, On a conjecture regarding primality of numbers constructed from prepending and appending identical digits, arXiv:1503.08883 [math.NT], 2015. EXAMPLE a(1) = 11. a(4) = 5: 5 151 31513 3315133, stop; height(5)=4. a(6)=16362: 16361 1163611 311636113 33116361133 3331163611333 333311636113333, stop; height(16361)=6. CROSSREFS Cf. A034276, A052205, A053600. Sequence in context: A184280 A266947 A157718 * A046210 A100757 A099677 Adjacent sequences:  A256954 A256955 A256956 * A256958 A256959 A256960 KEYWORD nonn,base,more AUTHOR Felice Russo, Jan 25 2000 EXTENSIONS Added a(10)-a(11) and corrected a(4) -  Chai Wah Wu, Apr 09 2015 Entry revised by N. J. A. Sloane, Apr 13 2015 STATUS approved

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Last modified October 20 21:30 EDT 2019. Contains 328273 sequences. (Running on oeis4.)