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: A003826 A127344 A058124 this_sequence A057074 A017412 A017532

Adjacent sequences: A015433 A015434 A015435 this_sequence A015437 A015438 A015439

nonn,easy

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