OFFSET
0,4
COMMENTS
Here, the term uniform used in the sense of Retakh, Serconek and Wilson. Graded is used in terms of Stanley's definition that all maximal chains have the same length n.
REFERENCES
R. Stanley, Enumerative combinatorics, Vol. 1, Cambridge University Press, Cambridge, 1997, pp. 96-100.
LINKS
V. Retakh, S. Serconek, and R. Wilson, Hilbert Series of Algebras Associated to Directed Graphs and Order Homology, arXiv:1010.6295 [math.RA], 2010-2011.
Wikipedia, Graded poset
Index entries for linear recurrences with constant coefficients, signature (8,-21,20,-5).
FORMULA
MATHEMATICA
Join[{0}, LinearRecurrence[{8, -21, 20, -5}, {0, 0, 2, 14}, 40]]
PROG
(Python)
def a(n, adict={0:0, 1:0, 2:0, 3:2, 4:14}):
if n in adict:
return adict[n]
adict[n]=8*a(n-1)-21*a(n-2)+20*a(n-3)-5*a(n-4)
return adict[n]
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
David Nacin, Feb 13 2012
STATUS
approved