0,2

If Y is a 3-subset of an 2n-set X then, for n>=4, a(n-2) is the number of 4-subsets of X having at least two elements in common with Y. - Milan R. Janjic (agnus(AT)blic.net), Dec 16 2007

G.f.: A(x) = (1+9*x+2*x^2)/(1-x)^3.

Cf. A000326, A049452, A033568.

Sequence in context: A088596 A077293 A053682 this_sequence A102085 A058968 A121805

Adjacent sequences: A033567 A033568 A033569 this_sequence A033571 A033572 A033573

nonn

njas