OFFSET
0,3
LINKS
G. C. Greubel, Table of n, a(n) for n = 0..1000
FORMULA
a(n) = (Sum_{k=0..n-1} (k+1)*Sum_{i=0..n-k-1} 2^i*binomial(n,n-k-i-1) * binomial(n+i-1,i))/n, n > 1, a(0)=0.
a(n) ~ sqrt(36+29*sqrt(6)) * (5+2*sqrt(6))^n / (50 * sqrt(Pi) * n^(3/2)). - Vaclav Kotesovec, Jun 08 2014
D-finite with recurrence: 2*n*a(n)-(30+19*n)*a(n+1)-(9+8*n)*a(n+2)+(n+3)*a(n+3)=0. - Robert Israel, Jan 07 2018
a(n) = Sum_{k=0..n-1} binomial(n-1,k)*hypergeom([k+1-n, n], [k+2], -2). - Peter Luschny, Jan 07 2018
O.g.f. A(x) = series reversion of x*(1 - x)/((1 + x)*(1 + 2*x)). - Peter Bala, Nov 08 2022
MAPLE
f:= gfun:-rectoproc({2*n*a(n)-(30+19*n)*a(n+1)-(9+8*n)*a(n+2)+(n+3)*a(n+3)=0, a(0)=0, a(1)=1, a(2)=4}, a(n), remember):
map(f, [$0..30]); # Robert Israel, Jan 07 2018
MATHEMATICA
CoefficientList[Series[(1-3*x-Sqrt[x^2-10*x+1])/(4*x+2), {x, 0, 20}], x] (* Vaclav Kotesovec, Jun 08 2014 *)
PROG
(Maxima)
a(n):=sum((k+1)*sum(2^i*binomial(n, n-k-i-1)*binomial(n+i-1, i), i, 0, n-k-1), k, 0, n-1)/n;
(PARI) my(x='x+O('x^50)); concat([0], Vec((1-3*x - sqrt(x^2-10*x+1))/(4*x + 2))) \\ G. C. Greubel, Jun 02 2017
CROSSREFS
KEYWORD
nonn,easy,changed
AUTHOR
Vladimir Kruchinin, Jun 08 2014
STATUS
approved