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 A109441 #27 Aug 15 2023 11:29:51
%S A109441 0,1,3,4,6,8,10,15,16,21,24,28,35,36,45,48,55,63,64,66,78,80,91,99,
%T A109441 100,105,120,136,143,144,153,168,171,190,195,196,210,224,231,253,255,
%U A109441 256,276,300,324,325,351,378,400,406,435,465,484,576,676,784,900
%N A109441 Sorted union of the numbers (k + 1)^2 - 1, (2*k + 1)*(2*k + 1 - 1)/2, (2*k)^2, (2*k)*(2*k - 1)/2 for k >= 0, with duplicates removed.
%t A109441 Union[Flatten[Table[{(n + 1)^2 - 1, (2*n + 1)*(2*n + 1 - 1)/2, (2*n)^2, (2*n)*(2*n - 1)/2}, {n, 0, 15}]]]
%K A109441 nonn,less
%O A109441 1,3
%A A109441 _Roger L. Bagula_, Jun 22 2007
%E A109441 Edited by _Georg Fischer_, Aug 14 2023