7,2

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: A031859 A061738 A104939 this_sequence A083608 A102277 A013692

Adjacent sequences: A015341 A015342 A015343 this_sequence A015345 A015346 A015347

sign,easy

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