OFFSET
1,3
COMMENTS
Based on equation (11) from the Cameron et al., reference.
LINKS
G. C. Greubel, Table of n, a(n) for n = 1..1000
P. Cameron, T. Prellberg and D. Stark, Asymptotics for incidence matrix classes, Electron. J. Combin. 13 (2006), #R85, p. 11.
FORMULA
a(n) = Sum_{k=0..2} C(C(n,2),k)*C(n,4-2*k).
a(n) = n^2*(n-1)*(5*n-7)/12.
G.f.: x^2*(1+7*x+2*x^2)/(1-x)^5.
MAPLE
a:= n-> (7+(5*n-12)*n)*n^2/12:
seq (a(n), n=1..40);
MATHEMATICA
Table[n^2*(n - 1)*(5*n - 7)/12, {n, 1, 50}] (* G. C. Greubel, Jun 28 2017 *)
PROG
(PARI) for(n=1, 25, print1(n^2*(n-1)*(5*n-7)/12, ", ")) \\ G. C. Greubel, Jun 28 2017
CROSSREFS
KEYWORD
nonn
AUTHOR
L. Edson Jeffery, Feb 29 2012
STATUS
approved