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 A291830 #7 Sep 03 2017 21:58:06
%S A291830 4,512,8748,16641,65536,312500,1119744,2130048,3294172,4787344,
%T A291830 5359225,8388608,19131876,36393867,40000000,77948684,143327232,
%U A291830 250994068,268468225,272646144,344882041,421654016,612780032,683437500,685980800,1073741824,1300078125
%N A291830 Numbers k such that k^4 is sum of two positive 7th powers.
%C A291830 When a^7 + b^7 = m, (ma)^7 + (mb)^7 = m^8 is 4th power.
%C A291830 When k in this sequence, k*(n^7) (n = 2, 3, ... ) is also in this sequence.
%e A291830 4^4 = 2^7 + 2^7, so 4 is in the sequence.
%e A291830 16641^4 = 129^7 + 358^7, so 16641 is in the sequence.
%t A291830 lst={};Do[If[IntegerQ[(n^4-a^7)^(1/7)],AppendTo[lst,n]],{n,1.4*10^9},{a,(n^4/2)^(1/7)}]; lst
%Y A291830 Cf. A000583, A001015, A000404, A009003, A050801.
%K A291830 nonn
%O A291830 1,1
%A A291830 _XU Pingya_, Sep 03 2017