12,2

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: A112431 A132908 A076254 this_sequence A034618 A015418 A018869

Adjacent sequences: A015429 A015430 A015431 this_sequence A015433 A015434 A015435

nonn,easy

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