OFFSET
0,2
FORMULA
G.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=-1).
Conjecture: (n+1)*a(n) +(-7*n+2)*a(n-1) +(7*n-5)*a(n-2) +(7*n-26)*a(n-3) +4*(-4*n+17)*a(n-4) +8*(n-5)*a(n-5)=0. - R. J. Mathar, Feb 18 2016
EXAMPLE
a(2)=2*1*3+2-1=7. a(3)=2*1*7+2+3^2+1-1=25. a(4)=2*1*25+2+2*3*7+2-1=95.
MAPLE
l:=-1: : k := 1 : m:=3: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