9,2

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: A124977 A128172 A050259 this_sequence A072018 A158726 A017409

Adjacent sequences: A015381 A015382 A015383 this_sequence A015385 A015386 A015387

sign,easy

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