2,2

a(n)=A091534(n, 4), n>=2.

a(n)= (3^(2*n))*(6*risefac(2/3, n)*risefac(1/3, n) - 4*n!*risefac(2/3, n) + risefac(4/3, n)*n!)/4!, with risefac(x, n)=Pochhammer(x, n).

E.g.f.: (6*hypergeom([2/3, 1/3], [], 9*x) - 4*hypergeom([1, 2/3], [], 9*x) + hypergeom([4/3, 1], [], 9*x) - 3)/4!.

a(n)= (6*fac3(3*n-2)*fac3(3*n-1)-4*fac3(3*n-1)*fac3(3*n)+fac3(3*n)*fac3(3*n+1))/4!, n>=2, with fac3(n)=A007661(n) (triple factorials). Rewritten from eq.12 of the Blasiak et al. reference given in A091534 for r=5, s=2, k=4.

Cf. A091539 (second column of array A091534 divided by 10).

Sequence in context: A031712 A108881 A031605 this_sequence A098250 A031515 A090890

Adjacent sequences: A091737 A091738 A091739 this_sequence A091741 A091742 A091743

nonn,easy

Wolfdieter Lang (wolfdieter.lang_AT_physik_DOT_uni-karlsruhe_DOT_de), Feb 13 2004