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 A322122 #17 Jan 28 2020 03:42:46
%S A322122 0,0,17,191,1816,16541,149320,1344880,12106148,108960347,980654368,
%T A322122 8825914594,79433288194,714899721602,6434097782077,57906880685893,
%U A322122 521161927629204,4690457351939133,42214116174823814,379927045590000351,3419343410347321718
%N A322122 Number of positive integers that are not the sum of 3 squares and a nonnegative (2n + 1)-st power.
%H A322122 Wikipedia, <a href="https://en.wikipedia.org/wiki/Legendre%27s_three-square_theorem">Legendre's three-square theorem</a>
%F A322122 a(n) = Sum_{k=2..n-1} (floor(3^(2n+1)/2^(2k+3)-7/8) + 1).
%t A322122 a[n_]:=Sum[Floor[3^(2n+1)/2^(2k+3)-7/8]+1, {k,2,n-1}];
%t A322122 Table[a[n], {n,21}]
%Y A322122 Cf. A004215, A297788, A273915, A297970, A296579, A299796.
%K A322122 nonn
%O A322122 1,3
%A A322122 _XU Pingya_, Nov 27 2018