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 A059284 #6 Jan 05 2017 02:54:34
%S A059284 1,1,3,11,47,219,1081,5557,29439,159611,881405,4940385,28035205,
%T A059284 160751005,929923395,5420717819,31809479855,187757573787,
%U A059284 1114012352029,6640357243537,39746256802185,238796968208537,1439587364576015
%N A059284 Right edge of triangle in A059283.
%H A059284 G. C. Greubel, <a href="/A059284/b059284.txt">Table of n, a(n) for n = 0..1000</a>
%F A059284 G.f.: -(-2+(-3*w^2-6*w+1)^(1/2))/(1+w)^2.
%t A059284 T[0,0] = 1; T[n_,0] = 0; T[n_, k_] /; 0 <= k <= n := T[n, k] = T[n, k - 1] + T[n - 1, k - 1] + T[n - 1, k] + T[n - 2, k - 1]; T[_, _] = 0; Table[T[n,n], {n,0,25}] (* _G. C. Greubel_, Jan 04 2016 *)
%Y A059284 Cf. A059283, A059226.
%K A059284 nonn
%O A059284 0,3
%A A059284 _N. J. A. Sloane_, Jan 24 2001