OFFSET
9,2
REFERENCES
J. Goldman and G.-C. Rota, The number of subspaces of a vector space, pp. 75-83 of W. T. Tutte, editor, Recent Progress in Combinatorics. Academic Press, NY, 1969.
I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 9..120
FORMULA
a(n) = Product_{i=1..9} ((-10)^(n-i+1)-1)/((-10)^i-1). - Vincenzo Librandi, Nov 04 2012
MATHEMATICA
Table[QBinomial[n, 9, -10], {n, 9, 20}] (* Vincenzo Librandi, Nov 04 2012 *)
PROG
(Magma) r:=9; q:=-10; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..20]]; // Vincenzo Librandi, Nov 04 2012
CROSSREFS
KEYWORD
sign,easy
AUTHOR
STATUS
approved
