3,2

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: A014943 A097836 A128917 this_sequence A099397 A093251 A135531

Adjacent sequences: A015268 A015269 A015270 this_sequence A015272 A015273 A015274

sign,easy

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