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 A182016 #6 Apr 09 2012 11:56:43
%S A182016 1,3,15,85,531,3545,24833,180251,1344163,10237001,79287469,622596063,
%T A182016 4945078477,39658283943,320689293119,2611817435525,21405148148051,
%U A182016 176396318594937,1460795339822349,12150467810552223,101463416752305385,850306144532133787
%N A182016 Central coefficients of triangle A182013.
%F A182016 a(n) = sum(M(i),i=n..2*n), where the M(n)'s are the Motzkin numbers.
%F A182016 Recurrence: a(n+1) = a(n) + M(2n+2) + M(2n+1) - M(n).
%t A182016 M[n_]:=If[n==0,1,Coefficient[(1+x+x^2)^(n+1),x^n]/(n+1)]; Table[Sum[M[i],{i,n,2n}],{n,0,40}]
%o A182016 (Maxima) M(n):=coeff(expand((1+x+x^2)^(n+1)),x^n)/(n+1);
%o A182016 makelist(sum(M(i),i,n,2*n),n,0,20);
%K A182016 nonn
%O A182016 0,2
%A A182016 _Emanuele Munarini_, Apr 06 2012