7,2

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: A122474 A048423 A122210 this_sequence A127881 A134857 A078871

Adjacent sequences: A015342 A015343 A015344 this_sequence A015346 A015347 A015348

sign,easy

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