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: A043680 A129478 A032749 this_sequence A083619 A073032 A140171

Adjacent sequences: A015350 A015351 A015352 this_sequence A015354 A015355 A015356

sign,easy

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