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 A132118 #15 Mar 26 2022 12:13:36
%S A132118 1,2,4,4,6,8,7,9,11,13,11,13,15,17,19,16,18,20,22,24,26,22,24,26,28,
%T A132118 30,32,34,29,31,33,35,37,39,41,43,37,39,41,43,45,47,49,51,53,46,48,50,
%U A132118 52,54,56,58,60,62,64,56,58,60,62,64,66,68,70,72,74,76
%N A132118 Triangle read by rows: T(n,k) = n*(n-1)/2 + 2*k - 1.
%H A132118 Andrew Howroyd, <a href="/A132118/b132118.txt">Table of n, a(n) for n = 1..1275</a> (rows 1..50)
%e A132118 First few rows of the triangle are:
%e A132118 1;
%e A132118 2, 4;
%e A132118 4, 6, 8;
%e A132118 7, 9, 11, 13;
%e A132118 11, 13, 15, 17, 19;
%e A132118 16, 18, 20, 22, 24, 26;
%e A132118 22, 24, 26, 28, 30, 32, 34;
%e A132118 29, 31, 33, 35, 37, 39, 41, 43;
%e A132118 ...
%t A132118 Table[(n(n-1))/2+2k-1,{n,20},{k,n}]//Flatten (* _Harvey P. Dale_, Mar 26 2022 *)
%Y A132118 Column 1 is A000124(n-1).
%Y A132118 Main diagonal is A034856.
%Y A132118 Row sums are A002411.
%K A132118 nonn,easy,tabl
%O A132118 1,2
%A A132118 _Gary W. Adamson_, Aug 10 2007
%E A132118 a(16), a(17) corrected by _Georg Fischer_, Jul 01 2020
%E A132118 Name changed and terms a(56) and beyond from _Andrew Howroyd_, Apr 17 2021