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 A099665 #17 Jun 29 2025 09:05:33
%S A099665 3,53,547,5531,55547,555523,5555527,55555553,555555541,5555555519,
%T A099665 55555555543,555555555551,5555555555551,55555555555541,
%U A099665 555555555555529,5555555555555539,55555555555555519,555555555555555487,5555555555555555533,55555555555555555483,555555555555555555491
%N A099665 a(n) is the largest prime before A002279(n).
%F A099665 a(n) = A007917(A002282(n)). - _Amiram Eldar_, Jun 29 2025
%e A099665 n=2: 53 is before 55.
%t A099665 Table[NextPrime[5*(10^n-1)/9, -1], {n, 1, 35}]
%t A099665 NextPrime[#,-1]&/@Table[FromDigits[PadRight[{},n,5]],{n,20}] (* _Harvey P. Dale_, Aug 31 2015 *)
%Y A099665 Cf. A002282, A003618, A003617, A007917, A096497, A096498, A068104, A002275-A002283, A099656-A099668.
%K A099665 base,nonn
%O A099665 1,1
%A A099665 _Labos Elemer_, Nov 17 2004