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 A119831 #4 Jan 19 2013 11:14:08
%S A119831 1,6,1,720,120,1,362880,60480,504,1,479001600,79833600,665280,1320,1,
%T A119831 1307674368000,217945728000,1816214400,3603600,2730,1,
%U A119831 6402373705728000,1067062284288000,8892185702400,17643225600,13366080,4896,1
%N A119831 Number triangle (3n)!/(3k)!.
%C A119831 Row sums are A087350. Inverse is bi-diagonal array A119832.
%F A119831 Number triangle T(n,k)=[k<=n]*(3n)!/(3k)!
%e A119831 Triangle begins
%e A119831 1,
%e A119831 6, 1,
%e A119831 720, 120, 1,
%e A119831 362880, 60480, 504, 1,
%e A119831 479001600, 79833600, 665280, 1320, 1,
%e A119831 1307674368000, 217945728000, 1816214400, 3603600, 2730, 1
%t A119831 Flatten[Table[(3n)!/(3k)!,{n,0,10},{k,0,n}]] (* _Harvey P. Dale_, Jan 19 2013 *)
%Y A119831 Cf. A119828.
%K A119831 easy,nonn,tabl
%O A119831 0,2
%A A119831 _Paul Barry_, May 25 2006