OFFSET
0,2
COMMENTS
"The corresponding (order-three) linear differential operator is not homomorphic to its adjoint, even with an algebraic extension." (see A. Bostan link) - Gheorghe Coserea, Aug 15 2016
LINKS
Vaclav Kotesovec, Table of n, a(n) for n = 0..100
A. Bostan, S. Boukraa, J.-M. Maillard, and J.-A. Weil, Diagonals of rational functions and selected differential Galois groups, arXiv preprint arXiv:1507.03227 [math-ph], 2015, Eq. (30).
FORMULA
a(n) = [(xyzuvw)^n] (1 - 9*x*y)/((1 - 3*y - 2*x + 3*y^2 + 9*x^2*y) * (1 - u - z) * (1 - v - w)).
D-finite with recurrence: n^3*a(n) -12*(3*n-2)*(-1+2*n)^2*a(n-1)=0. - R. J. Mathar, Mar 11 2016 [follows from the hypergeometric g.f. below - Georg Fischer, Jul 30 2022]
From Vaclav Kotesovec, Jul 01 2016: (Start)
a(n) = 3^(2*n) * (2*n)!^2 * Gamma(n + 1/3) / (Gamma(1/3) * (n!)^5).
a(n) ~ 12^(2*n)/(Gamma(1/3)*Pi*n^(5/3)).
(End)
From Gheorghe Coserea, Aug 16 2016: (Start)
a(n) = [(xyzuv)^n] 1/((1 - x + 3*y - 27*x*y^3 - 27*x*y^2 - 9*x*y + 3*y^2) * (1 - u - v - u*z - v*z)).
G.f.: hypergeom([1/3, 1/2, 1/2], [1, 1], 144*x).
(End)
EXAMPLE
1 + 12*x + 648*x^2 + 50400*x^3 + ...
MAPLE
A268549 := proc(n)
(1-9*x*y)/(1-3*y-2*x+3*y^2+9*x^2*y)/(1-u-z)/(1-v-w) ;
coeftayl(%, x=0, n) ;
coeftayl(%, y=0, n) ;
coeftayl(%, z=0, n) ;
coeftayl(%, u=0, n) ;
coeftayl(%, v=0, n) ;
coeftayl(%, w=0, n) ;
end proc:
seq(A268549(n), n=0..40) ; # R. J. Mathar, Mar 11 2016
series(hypergeom([1/3, 1/2, 1/2], [1, 1], 144*x), x=0, 14); # Gheorghe Coserea, Aug 15 2016
MATHEMATICA
FullSimplify[Table[3^(2*n)*(2*n)!^2*Gamma[n + 1/3]/(Gamma[1/3]*(n!)^5), {n, 0, 15}]] (* Vaclav Kotesovec, Jul 01 2016 *)
CROSSREFS
KEYWORD
nonn
AUTHOR
N. J. A. Sloane, Feb 29 2016
STATUS
approved