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: A084482 A034654 A015401 this_sequence A017410 A017530 A017004

Adjacent sequences: A015428 A015429 A015430 this_sequence A015432 A015433 A015434

nonn,easy

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