OFFSET
0,3
FORMULA
G.f.: (1-z)(1-z-q)/(z(3-3z-q)), where q = sqrt(1-6z+z^2).
D-finite with recurrence 2*(n+1)*a(n) +(-17*n+7)*a(n-1) +(37*n-59)*a(n-2) +(-37*n+89)*a(n-3) +(17*n-61)*a(n-4) +2*(-n+5)*a(n-5)=0. - R. J. Mathar, Jul 24 2022
EXAMPLE
Example: a(2)=2 because we have HH and UUDD.
CROSSREFS
KEYWORD
nonn
AUTHOR
Emeric Deutsch, Dec 28 2003
STATUS
approved