OFFSET
0,2
FORMULA
G.f f: f(z)=(1-sqrt(1-4*z*(a(0)-z*a(0)^2+z*a(1)+(k+l)*z^2/(1-z)+k*z^2/(1-z)^2)))/(2*z) (k=-1, l=0).
Conjecture: (n+1)*a(n) +(-7*n+2)*a(n-1) +(-n+11)*a(n-2) +(43*n-140)*a(n-3) +2*(-28*n+113)*a(n-4) +20*(n-5)*a(n-5)=0. - R. J. Mathar, Feb 21 2016
EXAMPLE
a(2)=2*1*5-2=8. a(3)=2*1*8-2+5^2-1=38. a(4)=2*1*38-2+2*5*8-2=152.
MAPLE
l:=0: : k := -1 : m:=5:d(0):=1:d(1):=m: for n from 1 to 30 do d(n+1):=sum(d(p)*d(n-p)+k, p=0..n)+l:od :
taylor((1-sqrt(1-4*z*(d(0)-z*d(0)^2+z*m+(k+l)*z^2/(1-z)+k*z^2/(1-z)^2)))/(2*z), z=0, 30); seq(d(n), n=0..30);
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
Richard Choulet, Apr 27 2010
STATUS
approved