4,2

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.

Adjacent sequences: A015291 A015292 A015293 this_sequence A015295 A015296 A015297

Sequence in context: A107538 A029829 A046835 this_sequence A097500 A061660 A035780

nonn,easy

Olivier Gerard (olivier.gerard(AT)gmail.com)