5,2

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: A031729 A001726 A109487 this_sequence A054258 A066871 A139675

Adjacent sequences: A015306 A015307 A015308 this_sequence A015310 A015311 A015312

sign,easy

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