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 A141434 #19 Apr 01 2021 17:27:27
%S A141434 0,0,3,0,6,10,0,9,16,21,0,12,22,30,36,0,15,28,39,48,55,0,18,34,48,60,
%T A141434 70,78,0,21,40,57,72,85,96,105,0,24,46,66,84,100,114,126,136,0,27,52,
%U A141434 75,96,115,132,147,160,171
%N A141434 Triangle T(n, k) = (k-1)*(3*n-k-1), read by rows.
%H A141434 G. C. Greubel, <a href="/A141434/b141434.txt">Rows n = 1..50 of the triangle, flattened</a>
%F A141434 Sum_{k=1..n} T(n,k) = (n-1)*n*(7*n-5)/6. - _R. J. Mathar_, Sep 07 2011
%e A141434 Triangle begins as:
%e A141434 0;
%e A141434 0, 3;
%e A141434 0, 6, 10;
%e A141434 0, 9, 16, 21;
%e A141434 0, 12, 22, 30, 36;
%e A141434 0, 15, 28, 39, 48, 55;
%e A141434 0, 18, 34, 48, 60, 70, 78;
%e A141434 0, 21, 40, 57, 72, 85, 96, 105;
%e A141434 0, 24, 46, 66, 84, 100, 114, 126, 136;
%e A141434 0, 27, 52, 75, 96, 115, 132, 147, 160, 171;
%p A141434 A141434:= (n,k) -> (k-1)*(3*n-k-1); seq(seq(A141434(n,k), k=1..n), n=1..12); # _G. C. Greubel_, Apr 01 2021
%t A141434 Table[(k-1)*(3*n-k-1), {n, 12}, {k, n}]//Flatten (* modified by _G. C. Greubel_, Apr 01 2021 *)
%o A141434 (Magma) [(k-1)*(3*n-k-1): k in [1..n], n in [1..12]]; // _G. C. Greubel_, Apr 01 2021
%o A141434 (Sage) flatten([[(k-1)*(3*n-k-1) for k in (1..n)] for n in (1..12)]) # _G. C. Greubel_, Apr 01 2021
%Y A141434 Cf. A255211 (row sums).
%K A141434 nonn,easy,tabl
%O A141434 1,3
%A A141434 _Roger L. Bagula_ and _Gary W. Adamson_, Aug 06 2008