A131298 - OEIS

%I #15 Jun 25 2023 03:44:43

%S 1,1,2,4,6,11,18,30,50,82,135,221,361,589,959,1560,2535,4116,6679,

%T 10832,17560,28457,46103,74674,120928,195802,316995,513148,830608,

%U 1344372,2175796,3521249,5698477

%N Diagonal sums of A104730.

%H <a href="/index/Rec#order_05">Index entries for linear recurrences with constant coefficients</a>, signature (1,2,0,-2,-1).

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

%F a(n) = Sum_{k=0..floor(n/2)} C(n-k+1,k) - C(k,n-2k+1).

%t LinearRecurrence[{1,2,0,-2,-1},{1,1,2,4,6},40] (* _Harvey P. Dale_, Aug 21 2021 *)

%Y Cf. A104730.

%K easy,nonn

%O 0,3

%A _Paul Barry_, Jun 26 2007