OFFSET
0,3
COMMENTS
Diagonal sums of number triangle A124369.
LINKS
Harvey P. Dale, Table of n, a(n) for n = 0..1000
Index entries for linear recurrences with constant coefficients, signature (0,2,3,1).
FORMULA
a(n)=sum{k=0..floor(n/2), sum{j=0..n-k, C(j,n-k-j)*C((j+k)/2,(j-k)/2)*(1+(-1)^(j-k))/2}}
a(0)=1, a(1)=0, a(2)=2, a(3)=3, a(n)=2*a(n-2)+3*a(n-3)+a(n-4). - Harvey P. Dale, Feb 11 2015
MATHEMATICA
CoefficientList[Series[1/(1-2x^2-3x^3-x^4), {x, 0, 40}], x] (* or *) LinearRecurrence[{0, 2, 3, 1}, {1, 0, 2, 3}, 40] (* Harvey P. Dale, Feb 11 2015 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Paul Barry, Oct 27 2006
STATUS
approved