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: A139265 A129311 A136048 this_sequence A124207 A068257 A086000

Adjacent sequences: A015270 A015271 A015272 this_sequence A015274 A015275 A015276

sign,easy

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