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 A047076 #12 Apr 03 2023 10:36:09
%S A047076 2,30203,133020331,1713302033171,12171330203317121,
%T A047076 151217133020331712151,1815121713302033171215181,
%U A047076 16181512171330203317121518161,331618151217133020331712151816133,9333161815121713302033171215181613339,11933316181512171330203317121518161333911
%N A047076 a(n+1) is the smallest palindromic prime containing exactly 2 more digits on each end than the previous term, with a(n) as a central substring.
%D A047076 Pickover, Clifford A., A Passion for Mathematics: Numbers, Puzzles, Madness, Religion and the Quest for Reality, John Wiley & Sons, Inc., Hoboken, New Jersey (2005) p. 108.
%H A047076 C. K. Caldwell, <a href="https://t5k.org/glossary/page.php?sort=PalindromicPrime">Palindromic Primes</a>
%t A047076 cc=If[EvenQ[First[#]],Reverse[#],#]&/@Tuples[{Range[0,9],Range[1,9,2]}]; nxt[n_]:=First[Select[Sort[FromDigits[Flatten[Join[{#,IntegerDigits[ n], Reverse[#]}]]]&/@cc],PrimeQ]]; NestList[nxt,2,10] (* _Harvey P. Dale_, Dec 24 2012 *)
%Y A047076 Cf. A053600.
%K A047076 base,fini,full,nice,nonn
%O A047076 1,1
%A A047076 _G. L. Honaker, Jr._, Jan 26 2000