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 A068898 #9 Sep 21 2024 17:36:44
%S A068898 55,66,2415,3003,5050,5151,5995,8778,9045,113050,138075,171405,174345,
%T A068898 177906,183921,198765,203203,216153,219453,234270,237705,239086,
%U A068898 252405,255255,266815,267546,275653,279378,284635,293761,294528,306153,309291,329266,348195
%N A068898 Triangular numbers containing 2k digits in which the sum of the first k digits = that of the rest.
%H A068898 Harvey P. Dale, <a href="/A068898/b068898.txt">Table of n, a(n) for n = 1..1000</a>
%e A068898 2415 is a term with 2+4 = 1+5.
%t A068898 dsQ[n_]:=Module[{idn=IntegerDigits[n],len=IntegerLength[n]/2}, Total[Take[ idn,len]] ==Total[ Take[idn,-len]]]; Select[Flatten[ Table[Table[(n(n+1))/2,{n,Ceiling[(Sqrt[8 10^i+1]-1)/2],Floor[ (Sqrt[8 10^(i+1)+1]-1)/2]}],{i,1,5,2}]],dsQ] (* _Harvey P. Dale_, Sep 29 2011 *)
%Y A068898 Intersection of A000217 and A240927.
%Y A068898 Cf. A068896, A068897.
%K A068898 easy,nonn,base
%O A068898 1,1
%A A068898 _Amarnath Murthy_, Mar 21 2002
%E A068898 Corrected and extended by _Harvey P. Dale_, Sep 29 2011
%E A068898 Offset changed by _Andrew Howroyd_, Sep 21 2024