9,2

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.

Sequence in context: A015312 A023333 A089315 this_sequence A043648 A035919 A023045

Adjacent sequences: A015372 A015373 A015374 this_sequence A015376 A015377 A015378

sign,easy

Olivier Gerard (ogerard(AT)ext.jussieu.fr)