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 A147723 #19 Oct 08 2017 05:59:53
%S A147723 1,0,1,0,3,1,0,18,6,1,0,117,45,9,1,0,765,342,81,12,1,0,5004,2556,702,
%T A147723 126,15,1,0,32733,18810,5859,1224,180,18,1,0,214119,136719,47493,
%U A147723 11241,1935,243,21,1
%N A147723 Riordan array (1, x(1 - 4x)/(1 - 7x + 3x^2)).
%C A147723 [0,3,3,1,0,0,0,....] DELTA [1,0,0,0,...] with Deléham DELTA as in A084938. A147723*A007318 is A147724.
%F A147723 G.f.: (1 - 7*x + 4*x^2)/(1 - (7+y)*x + (3+4*y)*x^2). - _Philippe Deléham_, Jan 11 2012
%F A147723 T(n,k) = 7*T(n-1,k) + T(n-1,k-1) - 3*T(n-2,k) - 4*T(n-2,k-1), T(0,0) = T(1,1) = T(2,2) = 1, T(1,0) = T(2,0) = 0, T(2,1) = 3, T(n,k) = 0 if k < 0 or if k > n. - _Philippe Deléham_, Nov 02 2013
%e A147723 Triangle begins
%e A147723 1;
%e A147723 0, 1;
%e A147723 0, 3, 1;
%e A147723 0, 18, 6, 1;
%e A147723 0, 117, 45, 9, 1;
%e A147723 0, 765, 342, 81, 12, 1;
%e A147723 ...
%t A147723 T[0,0] = T[1,1]= T[2,2] = 1; T[1,0] = T[2,0] = 0; T[2,1] = 3; T[n_, k_]:= If[k<0 || k>n, 0, 7 T[n - 1, k] + T[n - 1, k - 1] - 3 T[n - 2, k] - 4 T[n - 2, k - 1]]; Flatten[Table[ T[n, k], {n, 0, 8}, {k, 0, n}]] (* _Indranil Ghosh_, Mar 10 2017, after _Philippe Deléham_ *)
%o A147723 (PARI) T(n, k)= if(n==k, 1, if(k==0, 0, if(n==2 && k==1, 3, if(k<0 || k>n, 0, 7*T(n - 1, k) + T(n - 1, k - 1) - 3*T(n - 2, k) - 4*T(n - 2, k - 1)))));
%o A147723 {for(n=0, 8, for(k=0, n, print1(T(n,k),", ");); print();); } \\ _Indranil Ghosh_, Mar 10 2017
%Y A147723 Cf. A147720.
%K A147723 easy,nonn,tabl
%O A147723 0,5
%A A147723 _Paul Barry_, Nov 11 2008