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 A262633 #9 Oct 23 2015 13:41:23 %S A262633 0,101,31013,3310133,1023310133201,3331023310133201333, %T A262633 3223331023310133201333223,1133223331023310133201333223311, %U A262633 100311332233310233101332013332233113001,10231003113322333102331013320133322331130013201 %N A262633 Minimal nested base-4 palindromic primes with seed 0. %C A262633 Using only base-4 digits 0,1,2,3, 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 base-4 palindromic primes with seed s. %H A262633 Clark Kimberling, <a href="/A262633/b262633.txt">Table of n, a(n) for n = 1..300</a> %e A262633 a(3) = 31013 is the least base-4 prime having a(2) = 101 in its middle. Triangular format: %e A262633 0 %e A262633 101 %e A262633 31013 %e A262633 3310133 %e A262633 1023310133201 %e A262633 3331023310133201333, %t A262633 s = {0}; base = 4; z = 20; Do[NestWhile[# + 1 &, 1, ! PrimeQ[tmp = FromDigits[Join[#, IntegerDigits[Last[s]], Reverse[#]] &[IntegerDigits[#, base]], base]] &]; %t A262633 AppendTo[s, FromDigits[IntegerDigits[tmp, base]]], {z}]; s (* A262633 *) %t A262633 Map[FromDigits[ToString[#], base] &, s] (* A262634 *) %t A262633 (* _Peter J. C. Moses_, Sep 01 2015 *) %Y A262633 Cf. A261881 (base 10), A262634, A262627. Subsequence of A117699. %K A262633 nonn,base %O A262633 1,2 %A A262633 _Clark Kimberling_, Oct 02 2015