3,2

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: A031939 A134075 A002617 this_sequence A068261 A119520 A093634

Adjacent sequences: A015275 A015276 A015277 this_sequence A015279 A015280 A015281

sign,easy

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