

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
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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

Table of n, a(n) for n=1..11.
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



