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 A135057 #18 Apr 13 2025 15:01:21
%S A135057 25,2491,249919,24993439,2499984871,249999996751,24999999992431,
%T A135057 2499999999940951,249999999999995239,24999999999999996031,
%U A135057 2499999999999999964279,249999999999999999946639,24999999999999999997538239,2499999999999999999999854839,249999999999999999999999946639
%N A135057 Largest semiprime whose prime factors add up to 10^n.
%H A135057 Lekraj Beedassy, <a href="/A135057/b135057.txt">Table of n, a(n) for n = 1..35</a>
%F A135057 a(n) = A124450(n)*(10^n - A124550(n)) {= A137611(n)*A137612(n) for n>1}.
%F A135057 a(n) = 100^n/4-(A124049(n))^2. - _Zak Seidov_, Feb 15 2008
%t A135057 s={};f[{p_,e_}]:=e*p;Do[a=(10^n/2)^2;While[PrimeOmega[a]!=2||Total[f/@FactorInteger[a]]!=10^n,a=a-1];AppendTo[s,a],{n,11}];s (* _James C. McMahon_, Apr 13 2025 *)
%K A135057 nonn
%O A135057 1,1
%A A135057 _Lekraj Beedassy_, Feb 11 2008