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 A072723 #4 Mar 24 2023 10:42:03
%S A072723 1,15,16764334957,3079163563531047898532266016633501
%N A072723 Integers which are exactly the concatenation of the first m odd numbers (A019519) divided by their sum (A000290 = m^2).
%C A072723 A probability argument suggests that this sequence may be finite.
%e A072723 a(1) = 1/1 = 1; a(2) = 135/(1+3+5) = 15; a(3) = 1357911131517/(1+3+5+7+9+11+13+15+17) = 16764334957; a(4) = 1357911131517192123252729313335373941/(1+3+5+7+9+11+13+15+17+19+21+23+25+27+29+31+33+35+37+39+41) = 3079163563531047898532266016633501.
%t A072723 Select[Table[FromDigits[Flatten[IntegerDigits/@Range[1,2n+1,2]]]/Total[Range[1,2n+1,2]],{n,0,30}],IntegerQ] (* _Harvey P. Dale_, Mar 24 2023 *)
%Y A072723 Cf. A067122, A072724, A072725.
%K A072723 base,nonn
%O A072723 1,2
%A A072723 _Henry Bottomley_, Jul 06 2002