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 A262195 #26 Apr 15 2025 11:58:59
%S A262195 150401,13628801,136288001,113076743680001
%N A262195 Primes that are the concatenation of 1, k! and 1, for some integer k.
%C A262195 Inspired by A089764.
%C A262195 The next term is associated with k = 21225 and has 82625 digits, so it is too large to include here. See A381040. - _Michael S. Branicky_, Apr 15 2025
%e A262195 For n = 1, k = 7, 7! = 5040, and a(1) = 150401 is a prime number.
%t A262195 Select[Table[FromDigits[Flatten[{(1), IntegerDigits[n!], {1}}]], {n, 1000}], PrimeQ] (* _Vincenzo Librandi_, Sep 15 2015 *)
%o A262195 (PARI) for(n=1, 1e3, if(isprime(k=eval(Str(1,n!,1))), print1(k", ")))
%o A262195 (Magma) [m: n in [1..1000] | IsPrime(m) where m is Seqint(Intseq(1) cat Intseq(Factorial(n)) cat Intseq(1))]; // _Vincenzo Librandi_, Sep 15 2015
%Y A262195 Cf. A089764, A381040 (corresponding k).
%K A262195 nonn,base
%O A262195 1,1
%A A262195 _Altug Alkan_, Sep 14 2015