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: A123563 A043475 A061544 this_sequence A116331 A099650 A077578

Adjacent sequences: A015273 A015274 A015275 this_sequence A015277 A015278 A015279

sign,easy

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