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 A308899 #31 May 09 2021 13:34:35
%S A308899 2,29,131,33287,17627,1754975809,59218567,318879703697,
%T A308899 2030507011013017019023,14400758943354730631369,1016015647,
%U A308899 32002443156997,2464082401591041689,4916481866859605372937116297910511,2030507011013017019023029031037041043047
%N A308899 a(n) = largest prime factor of the number with decimal expansion 20305070...0p_n where p_n = n-th prime.
%C A308899 The Honaker-Caldwell link gives a(25) =
%C A308899 20305070110130170190230290310370410430470530590
%C A308899 \61067071073079083089097,
%C A308899 with 70 digits.
%H A308899 Daniel Suteu, <a href="/A308899/b308899.txt">Table of n, a(n) for n = 1..43</a>
%H A308899 G. L. Honaker, Jr. and Chris Caldwell, <a href="https://primes.utm.edu/curios/page.php?number_id=129">Prime Curios!, 2030507...[70 digits]...89097.</a>
%e A308899 Here are Maple's factorizations of 2, 203, 20305, ... (the factors appear in random order):
%e A308899 2 = (2)
%e A308899 203 = (7) (29)
%e A308899 20305 = (5) (31) (131)
%e A308899 2030507 = (61) (33287)
%e A308899 2030507011 = (13) (17627) (8861)
%e A308899 2030507011013 = (13) (89) (1754975809)
%e A308899 2030507011013017 = (59218567) (34288351)
%e A308899 2030507011013017019 = (7) (547) (1663) (318879703697)
%t A308899 Table[FactorInteger[FromDigits[Flatten[IntegerDigits/@Riffle[Prime[Range[n]],0]]]][[-1,1]],{n,20}] (* _Harvey P. Dale_, May 09 2021 *)
%o A308899 (PARI) pp = 0; forprime (p=2, 47, print1 (vecmax(factor(pp = pp * 10^(1+#digits(p)) + p)[,1]~) ", ")) \\ _Rémy Sigrist_, Jul 13 2019
%Y A308899 Inspired by the comment in _Bernard Schott_'s A309101.
%K A308899 nonn,base
%O A308899 1,1
%A A308899 _N. J. A. Sloane_, Jul 13 2019
%E A308899 More terms from _Rémy Sigrist_, Jul 13 2019