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 A230561 #22 Mar 14 2015 10:11:10 %S A230561 2,50,87539319 %N A230561 Smallest number that is the sum of two positive n-th powers in >= n ways. %C A230561 Guy, 2004: "Euler knew that 635318657 = 133^4 + 134^4 = 59^4 + 158^4, and Leech showed this to be the smallest example. No one knows of three such equal sums." Thus no one knows whether a(4) exists, which requires four such equal sums. %C A230561 a(4) > 10^21 (if it exists). There is no number <= 10^21 that is the sum of two positive 4th powers in >= three ways. - _Donovan Johnson_, Jan 07 2014 %D A230561 R. K. Guy, Unsolved Problems in Number Theory, 3rd edition, Springer, 2004, D1. %F A230561 a(n) >= A016078(n) for n > 1, with equality at least for n = 2, and inequality at least for n = 3. %e A230561 2 = 1^1 + 1^1. %e A230561 50 = 1^2 + 7^2 = 5^2 + 5^2. %e A230561 87539319 = 167^3 + 436^3 = 228^3 + 423^3 = 255^3 + 414^3. %Y A230561 Cf. A048610, A011541 for a(2), a(3). %Y A230561 Cf. also A016078, A230477. %K A230561 hard,more,nonn,bref %O A230561 1,1 %A A230561 _Jonathan Sondow_, Oct 23 2013