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 A174169 #9 Dec 12 2013 19:03:42
%S A174169 1,1,-1,-2,0,0,-3,1,8,1,1,26,7,-51,-3,0,-264,-186,348,-120,-285,2697,
%T A174169 2871,-2304,3393,8029,-25795,-36872,16108,-60010,-159683,213795,
%U A174169 413712,-181857,833779,2669534,-1272977,-4030235,3611168,-9145271,-39467427
%N A174169 A generalized Chebyshev transform of the Motzkin numbers A001006.
%C A174169 Hankel transform is the (1,3) Somos-4 sequence A174170.
%F A174169 G.f.: (1-x+3x^2-sqrt(1-2x+3x^2-6x^3+9x^4))/(2x^2)=(1/(1+3x))*M(x/(1+3x^2)), M(x) the g.f. of A010006;
%F A174169 a(n) = sum{k=0..floor(n/2), (-3)^k*A001006(n-2k)}.
%F A174169 Conjecture: (n+2)*a(n) -(2*n+1)*a(n-1) +3*(n-1)*a(n-2) +3*(5-2*n)*a(n-3) +9*(n-4)*a(n-4)=0. - _R. J. Mathar_, Sep 30 2012
%K A174169 easy,sign
%O A174169 0,4
%A A174169 _Paul Barry_, Mar 10 2010