OFFSET
0,1
COMMENTS
If Y is a 5-subset of an n-set X then, for n>=11, a(n-11) is the number of 7-subsets of X having at most one element in common with Y. > - Milan Janjic, Dec 08 2007
LINKS
Index entries for linear recurrences with constant coefficients, signature (8, -28, 56, -70, 56, -28, 8, -1).
FORMULA
G.f.: (5-4*x)/(1-x)^8.
a(n)= (n+35)*binomial(n+6, 6)/7 = 5*b(n)-4*b(n-1), with b(n):=A000580(n+7)=binomial(n+7, 7).
a(0)=5, a(1)=36, a(2)=148, a(3)=456, a(4)=1170, a(5)=2640, a(6)=5412, a(7)=10296, a(n)=8*a(n-1)-28*a(n-2)+56*a(n-3)-70*a(n-4)+56*a(n-5)- 28*a(n-6)+ 8*a(n-7)-a(n-8). - Harvey P. Dale, Aug 16 2014
MATHEMATICA
CoefficientList[Series[(5-4*x)/(1-x)^8, {x, 0, 30}], x] (* or *) LinearRecurrence[{8, -28, 56, -70, 56, -28, 8, -1}, {5, 36, 148, 456, 1170, 2640, 5412, 10296}, 30] (* Harvey P. Dale, Aug 16 2014 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Wolfdieter Lang, Jul 16 2004
STATUS
approved