This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A262651 #6 Oct 31 2015 15:03:02 %S A262651 3,11311,121131121,5312113112135,14531211311213541, %T A262651 1145312113112135411,51114531211311213541115, %U A262651 5511145312113112135411155,50551114531211311213541115505,115055111453121131121354111550511,51150551114531211311213541115505115 %N A262651 Minimal nested palindromic base-6 primes with seed 3; see Comments. %C A262651 Using only base-6 digits 0,1,2,3,4,5, 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-6 primes with seed s. %H A262651 Clark Kimberling, <a href="/A262651/b262651.txt">Table of n, a(n) for n = 1..300</a> %e A262651 a(3) = 121131121 is the least base-6 prime having a(2) = 11311 in its middle. Triangular format: %e A262651 3 %e A262651 11311 %e A262651 121131121 %e A262651 5312113112135 %e A262651 14531211311213541 %t A262651 s = {3}; base = 6; z = 20; Do[NestWhile[# + 1 &, 1, ! PrimeQ[tmp = FromDigits[Join[#, IntegerDigits[Last[s]], Reverse[#]] &[IntegerDigits[#, base]], base]] &]; %t A262651 AppendTo[s, FromDigits[IntegerDigits[tmp, base]]], {z}]; s (* A262651 *) %t A262651 Map[FromDigits[ToString[#], base] &, s] (* A262652 *) %t A262651 (* _Peter J. C. Moses_, Sep 01 2015 *) %Y A262651 Cf. A261881 (base 10), A262652, A262627. %K A262651 nonn,easy,base %O A262651 1,1 %A A262651 _Clark Kimberling_, Oct 27 2015