OFFSET
1,2
COMMENTS
Using only base-7 digits 0,1,2,3,4,5,6 let s be a palindrome and put a(1) = s. Let a(2) be the least palindromic prime having s in the middle; for n > 2, let a(n) be the least palindromic prime have a(n-1) in the middle. Then (a(n)) is the sequence of minimal nested palindromic base-7 primes with seed s.
LINKS
Clark Kimberling, Table of n, a(n) for n = 1..300
EXAMPLE
a(3) = 42124 is the least base-7 prime having a(2) = 212 in its middle. Triangular format:
1
212
42124
204212402
2220421240222
222204212402222
2222220421240222222
MATHEMATICA
s = {1}; base = 7; z = 20; Do[NestWhile[# + 1 &, 1, ! PrimeQ[tmp = FromDigits[Join[#, IntegerDigits[Last[s]], Reverse[#]] &[IntegerDigits[#, base]], base]] &];
AppendTo[s, FromDigits[IntegerDigits[tmp, base]]], {z}]; s (* A262657 *)
Map[FromDigits[ToString[#], base] &, s] (* A262658 *)
(* Peter J. C. Moses, Sep 01 2015 *)
CROSSREFS
KEYWORD
nonn,easy,base
AUTHOR
Clark Kimberling, Oct 27 2015
STATUS
approved