4,2

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: A034622 A004046 A107119 this_sequence A046710 A093180 A093181

Adjacent sequences: A015300 A015301 A015302 this_sequence A015304 A015305 A015306

nonn,easy

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