5,2

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: A105989 A020445 A064195 this_sequence A043587 A043791 A043805

Adjacent sequences: A015305 A015306 A015307 this_sequence A015309 A015310 A015311

sign,easy

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