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 A124821 #6 Jul 07 2020 07:47:31 %S A124821 1,-2,1,7,-5,1,-30,25,-8,1,143,-130,52,-11,1,-728,700,-320,88,-14,1, %T A124821 3876,-3876,1938,-627,133,-17,1,-21318,21945,-11704,4235,-1078,187, %U A124821 -20,1,120175,-126500,70840,-27830,8050,-1700 %N A124821 Number triangle T(n,k)=(-1)^(n-k)*(3k+2)*C(3n+1, n-k)/(2n+k+2). %C A124821 Inverse of number triangle A124819. Row sums are (-1)^n*A001764(n). %H A124821 Paul Drube, <a href="https://arxiv.org/abs/2007.01892">Generalized Path Pairs and Fuss-Catalan Triangles</a>, arXiv:2007.01892 [math.CO], 2020. See Figure 4 p. 8. (up to signs). %e A124821 Triangle begins %e A124821 1, %e A124821 -2, 1, %e A124821 7, -5, 1, %e A124821 -30, 25, -8, 1, %e A124821 143, -130, 52, -11, 1, %e A124821 -728, 700, -320, 88, -14, 1, %e A124821 3876, -3876, 1938, -627, 133, -17, 1 %Y A124821 Cf. A124019. %K A124821 easy,sign,tabl %O A124821 0,2 %A A124821 _Paul Barry_, Nov 08 2006