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 A084669 #16 Sep 08 2022 08:45:11
%S A084669 53,239,6719,7321,15737,30763,38977,41981,44987,587107,661121,751133,
%T A084669 1051177,1229201,1297211,1303213,1327217,1823281,1913293,1999303,
%U A084669 2131321,2179327,2207329,2239333,2371351,2689391,2699393,3067439
%N A084669 Primes which are a concatenation of prime(n) and n.
%e A084669 a(2)=239 because prime[9]=23 and concatenation of 23 and 9 is 239 which is prime.
%t A084669 Select[Table[FromDigits[Flatten[{IntegerDigits[Prime[n]], IntegerDigits[n]}]], {n, 1, 500}], PrimeQ]
%o A084669 (Magma) [p: n in [1..500] | IsPrime(p) where p is Seqint(Intseq(n) cat Intseq(NthPrime(n)))]; // _Bruno Berselli_, Sep 15 2015
%Y A084669 Cf. A084667.
%Y A084669 Subsequence of primes of A075110.
%K A084669 nonn,base
%O A084669 1,1
%A A084669 _Zak Seidov_, Jun 29 2003