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 A257840 #17 Jul 03 2022 22:09:36
%S A257840 0,0,4,3,4,7,15,7,10,16,34,13,18,29,61,21,30,46,96,31,43,67,139,43,60,
%T A257840 92,190,57,78,121,249,73,100,154,316,91,124,191,391,111,154,232,474,
%U A257840 133,181,277,565,157,99,326,664,183,248,379,771,211,286,436,886,241,326,497,1009,273,370,562,1140,307,415,631,1279,343,210,704,1426,381,514,781,1581,421
%N A257840 y-value of the lexicographically first integer solution (x,y,z) of 4/n = 1/x + 1/y + 1/z with 0 < x < y < z, or 0 if there is no such solution. Corresponding x and z values are in A257839 and A257841.
%C A257840 See A073101 for more details.
%C A257840 This differs from A075246 starting with a(89)=690 vs A075246(89)=306, corresponding to the representations 4/89 = 1/23 + 1/690 + 1/61410 = 1/24 + 1/306 + 1/108936.
%H A257840 M. F. Hasler, <a href="/A257840/b257840.txt">Table of n, a(n) for n = 1..1000</a>
%o A257840 (PARI) apply( {A257840(n, t)=for(x=n\4+1, 3*n\4, for(y=max(1\t=4/n-1/x, x)+1, ceil(2/t)-1, numerator(t-1/y)==1 && return(y)))}, [1..99]) \\ improved by _M. F. Hasler_, Jul 03 2022
%Y A257840 Cf. A073101, A075245, A075246, A075247.
%K A257840 nonn
%O A257840 1,3
%A A257840 _M. F. Hasler_, May 16 2015