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 A172998 #7 Jun 13 2017 10:22:07
%S A172998 1,2,3,4,372
%N A172998 Numbers n such that 10^4n + 10^3n - 10^n - 3 is prime.
%C A172998 Corresponds to the numbers 10987, 100999897, 1000999998997, 10000999999989997, ...
%t A172998 fQ[n_] := PrimeQ[10^(4 n) + 10^(3 n) - 10^n - 3]; k = 1; lst = {}; While[k < 3300, If[ fQ@k, AppendTo[lst, k]]; k++ ]; lst (* _Robert G. Wilson v_, Feb 15 2010 *)
%o A172998 (PARI) is(n)=ispseudoprime(10^4*n+10^3*n-10^n-3) \\ _Charles R Greathouse IV_, Jun 13 2017
%K A172998 nonn
%O A172998 1,2
%A A172998 _James G. Merickel_, Feb 07 2010