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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, 14736384418081448363741
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.
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
KEYWORD
nonn,base,more,changed
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
a(12) from Michael S. Branicky, Oct 28 2024
STATUS
approved