OFFSET
6,1
COMMENTS
Number of {T_1,T_2,...,T_k} where T_i,i=1..k are 3-subsets of an n-set such that {D | D is 2-subset of T_i for some i=1..k} has l elements; k=4,l=11.
REFERENCES
V. Jovovic, On the number of two-dimensional simplicial complexes (in Russian), Metody i sistemy tekhnicheskoy diagnostiki, Vypusk 16, Mezhvuzovskiy zbornik nauchnykh trudov, Izdatelstvo Saratovskogo universiteta, 1991.
LINKS
T. D. Noe, Table of n, a(n) for n = 6..1000
FORMULA
a(n) = 360*C(n, 6)+10710*C(n, 7)+42000*C(n, 8)+41580*C(n, 9)+12600*C(n, 10) = n*(n-1)*(n-2)*(n-3)*(n-4)*(n-5)*(n^4+3*n^3-58*n^2-120*n+1008)/288.
Empirical G.f.: -30*x^6*(89*x^4-391*x^3+401*x^2+309*x+12)/(x-1)^11. [Colin Barker, Jun 22 2012]
CROSSREFS
KEYWORD
nonn
AUTHOR
Vladeta Jovovic, Apr 16 2000
EXTENSIONS
More terms from James A. Sellers, Apr 16 2000
STATUS
approved