OFFSET
0,2
LINKS
Alois P. Heinz, Table of n, a(n) for n = 0..1000
FORMULA
G.f.: (43*x^3+31*x^2+19*x+12)*x/(1-x)^9.
a(n) = n*(n+1)*(n+2)*(n+3)*(n+4)*(15*n^3+30*n^2+245*n+286)/5760.
EXAMPLE
a(1) = 12 = 4!/2: (1-2-3-4-5-1), (1-2-3-5-4-1), (1-2-4-3-5-1), (1-2-4-5-3-1), (1-2-5-3-4-1), (1-2-5-4-3-1), (1-3-2-4-5-1), (1-3-2-5-4-1), (1-3-4-2-5-1), (1-3-5-2-4-1), (1-4-2-3-5-1), (1-4-3-2-5-1).
MAPLE
a:= n-> (6864+(20180+(22980+(13295+(4536+(1070+(180+15*n)*
n)*n)*n)*n)*n)*n)*n/5760:
seq(a(n), n=0..40);
CROSSREFS
KEYWORD
nonn
AUTHOR
Alois P. Heinz, Aug 23 2012
STATUS
approved