%I #13 Aug 03 2017 03:01:51

%S 1,1,2,5,6,13,17,29,43,64,100,144,223,326,492,733,1089,1634,2421,3626,

%T 5389,8041,11985,17847,26624,39640,59112,88059,131242,195592,291433,

%U 434369,647218,964581,1437374,2142013,3192113,4756821

%N a(n) = Sum_{k=floor((n+1)/2)..n} T(k,n-k); i.e., a(n) is the n-th diagonal sum of left-justified array T given by A026998.

%H Vincenzo Librandi, <a href="/A027010/b027010.txt">Table of n, a(n) for n = 1..1000</a>

%F G.f.: x*(2x^3-x^2+1)/((1-x)*(1-2x^2-x^3+x^4)).

%t CoefficientList[Series[(2 x^3 - x^2 + 1) / ((1 - x) (1 - 2 x^2 - x^3 + x^4)), {x, 0, 40}], x] (* _Vincenzo Librandi_, Aug 03 2017 *)

%K nonn

%O 1,3

%A _Clark Kimberling_