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 A335821 #20 Apr 05 2025 03:03:13
%S A335821 0,1,0,4,3,0,9,8,5,0,16,15,12,7,0,25,24,21,16,9,0,36,35,32,27,20,11,0,
%T A335821 49,48,45,40,33,24,13,0,64,63,60,55,48,39,28,15,0,81,80,77,72,65,56,
%U A335821 45,32,17,0,100,99,96,91,84,75,64,51,36,19,0,121,120,117,112,105,96,85,72,57,40,21,0
%N A335821 Triangular array T(n, k) = n^2 - k^2, read by rows.
%e A335821 The triangle begins:
%e A335821 n\k 0 1 2 3 4 5 6 7 8 9
%e A335821 0 0
%e A335821 1 1 0
%e A335821 2 4 3 0
%e A335821 3 9 8 5 0
%e A335821 4 16 15 12 7 0
%e A335821 5 25 24 21 16 9 0
%e A335821 6 36 35 32 27 20 11 0
%e A335821 7 49 48 45 40 33 24 13 0
%e A335821 8 64 63 60 55 48 39 28 15 0
%e A335821 9 81 80 77 72 65 56 45 32 17 0
%t A335821 Table[(n^2 - k^2), {n, 0, 11}, {k, 0, n}] // Flatten (* _Michael De Vlieger_, Jun 28 2020 *)
%Y A335821 Cf. A257238.
%K A335821 nonn,tabl,easy
%O A335821 0,4
%A A335821 _Mokhtar Mohamed_, Jun 25 2020