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: A060792 A119519 A131645 this_sequence A043516 A046410 A098936

Adjacent sequences: A015307 A015308 A015309 this_sequence A015311 A015312 A015313

sign,easy

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