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 A216284 #15 Aug 28 2017 09:22:25 %S A216284 0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0, %T A216284 0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0, %U A216284 0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,1,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0,0 %N A216284 Number of solutions to the equation x^4+y^4 = n with x >= y > 0. %H A216284 Antti Karttunen, <a href="/A216284/b216284.txt">Table of n, a(n) for n = 1..65537</a> %F A216284 a(n) <= A216280(n). - _Antti Karttunen_, Aug 28 2017 %e A216284 From _Antti Karttunen_, Aug 28 2017: (Start) %e A216284 For n = 2 there is one solution: 2 = 1^4 + 1^4, thus a(2) = 1. %e A216284 For n = 17 there is one solution: 17 = 2^4 + 1^4, thus a(17) = 1. %e A216284 For n = 635318657 we have two solutions: 635318657 = 158^4 + 59^4 = 134^4 + 133^4, thus a(635318657) = 2. Note that this is the first point where the sequence attains value greater than 1. See _Charles R Greathouse IV_'s Jan 12 2017 comment in A216280. %e A216284 (End) %o A216284 (Scheme) (define (A216284 n) (let loop ((x (A255270 n)) (s 0)) (let* ((x4 (A000583 x)) (y4 (- n x4))) (if (< x4 y4) s (loop (- x 1) (+ s (if (and (> y4 0) (= (A000583 (A255270 y4)) y4)) 1 0))))))) ;; _Antti Karttunen_, Aug 28 2017 %Y A216284 Cf. A025455, A025446, A000161, A025426, A216280. %K A216284 nonn %O A216284 1,635318657 %A A216284 _V. Raman_, Sep 03 2012 %E A216284 Definition edited to match the given data and the second part of offset (635318657) explicitly added by _Antti Karttunen_, Aug 28 2017