A091551 - OEIS

%I #5 Oct 12 2012 14:40:20

%S 1,228,83232,46854720,38109367296,42479241412608,62290218157719552,

%T 116373513947009679360,270010358636135897235456,

%U 762020881523854021734432768,2571195906705444158241905836032

%N Second column (k=3) sequence of array ((7,2)-Stirling2) divided by 14.

%F a(n)= product(5*j+2, j=0..n-1)*(-3*product(5*j+1, j=0..n-1) + product(5*j+3, j=0..n-1))/(3!*14), n>=2. From eq.12 of the Blasiak et al. reference given in A007840 with r=7, s=2, k=3.

%F a(n)= (5^(2*n))*risefac(2/5, n)*(-3*risefac(1/5, n) + risefac(3/5, n))/(3!*14), n>=2, with risefac(x, n)=Pochhammer(x, n).

%F E.g.f.: (hypergeom([2/5, 3/5], [], 25*x) - 3*hypergeom([1/5, 2/5], [], 25*x) + 2)/(3!*14).

%Y Cf. A091550 (second column of (6, 2)-Stirling2 array), A091552 (second column of (8, 2)-Stirling2 array).

%K nonn,easy

%O 0,2

%A _Wolfdieter Lang_, Feb 13 2004