login
Expansion of (1+2x^2)/((1-x)^2(1+x^2)^2).
1

%I #5 Oct 01 2023 20:25:13

%S 1,2,3,4,4,4,6,8,7,6,9,12,10,8,12,16,13,10,15,20,16,12,18,24,19,14,21,

%T 28,22,16,24,32,25,18,27,36,28,20,30,40,31,22,33,44,34,24,36,48,37,26,

%U 39,52,40,28,42,56,43,30,45,60,46,32,48,64,49,34,51,68,52,36,54,72,55

%N Expansion of (1+2x^2)/((1-x)^2(1+x^2)^2).

%C Row sums of triangle A108358.

%H <a href="/index/Rec#order_06">Index entries for linear recurrences with constant coefficients</a>, signature (2, -3, 4, -3, 2, -1).

%F a(n)=2a(n-1)-3a(n-2)+4a(n-3)-3a(n-4)+2a(n-5)-a(n-6); a(n)=-cos(pi*n/2)/4+(1-n)*sin(pi*n/2)/4+(3n+5)/4; a(n)=sum{k=0..n, mod(sum{j=0..n-k, C(k, j)C(n-j, k)floor((j+2)/2)}, 2)}

%K easy,nonn

%O 0,2

%A _Paul Barry_, May 31 2005