login
Diagonal sums of a Chebyshev number triangle.
1

%I #6 Mar 30 2012 18:59:02

%S 1,0,0,1,3,3,8,30,117,466,1960,8655,40391,200085,1051888,5844844,

%T 34131049,208344660,1324262256,8743620525,59891078347,425216195191,

%U 3126418416440,23778261543210,186815245299549,1513931016854598

%N Diagonal sums of a Chebyshev number triangle.

%C Diagonal sums of number triangle A101124.

%H <a href="/index/Ch#Cheby">Index entries for sequences related to Chebyshev polynomials.</a>

%F a(n)=sum{k=0..floor(n/2), if(k<n-k, T(n-2k, k), if(k=n-k, 1, 0))} where T(n, k)=(n/2)sum{j=0..floor(n/2), C(n-j, j)(-1)^j*(2k)^(n-2j)}.

%K easy,nonn

%O 0,5

%A _Paul Barry_, Dec 02 2004