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 A038394 #30 Feb 17 2024 10:30:47
%S A038394 2,32,532,7532,117532,13117532,1713117532,191713117532,23191713117532,
%T A038394 2923191713117532,312923191713117532,37312923191713117532,
%U A038394 4137312923191713117532,434137312923191713117532,47434137312923191713117532,5347434137312923191713117532
%N A038394 Concatenate first n primes in reverse order.
%D A038394 F. Smarandache, Sequences of Numbers Involved in Unsolved Problems, Hexis, Phoenix, 2006.
%H A038394 Reinhard Zumkeller, <a href="/A038394/b038394.txt">Table of n, a(n) for n = 1..300</a>
%H A038394 Mihaly Bencze [Beneze] and L. Tutescu, editors, <a href="http://www.gallup.unm.edu/~smarandache/snaqint2.txt">Some Notions and Questions in Number Theory, Vol. II</a>.
%H A038394 M. Fleuren, <a href="http://www.gallup.unm.edu/~smarandache/SmBackConPri.txt">Smarandache Back Concatenated Primes</a>.
%H A038394 F. Smarandache, <a href="http://www.gallup.unm.edu/~smarandache/Sequences-book.pdf">Sequences of Numbers Involved in Unsolved Problems</a>.
%t A038394 Join[{s = 2}, Table[s = FromDigits[Flatten[IntegerDigits[{Prime[n], s}]]], {n, 2, 13}]] (* _Jayanta Basu_, Jul 14 2013 *)
%o A038394 (Haskell)
%o A038394 a038394 n = a038394_list !! (n-1)
%o A038394 a038394_list = f "" a000040_list where
%o A038394 f xs (q:qs) = (read ys :: Integer) : f ys qs
%o A038394 where ys = show q ++ xs
%o A038394 -- _Reinhard Zumkeller_, Mar 03 2014
%o A038394 (PARI) a(n) = fromdigits(concat([digits(p) | p<-Vecrev(primes(n))])); \\ _Andrew Howroyd_, Aug 29 2020
%Y A038394 Cf. A000040, A000422, A019518.
%K A038394 nonn,base
%O A038394 1,1
%A A038394 M. I. Petrescu (mipetrescu(AT)yahoo.com)
%E A038394 Offset corrected by _Reinhard Zumkeller_, Mar 03 2014