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 A015255 Gaussian binomial coefficient [ n,2 ] for q = -5. 3
 1, 21, 546, 13546, 339171, 8476671, 211929796, 5298179796, 132454820421, 3311368882921, 82784230211046, 2069605714586046, 51740143068101671, 1293503575685289171, 32337589397218492296, 808439734905030992296 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,2 REFERENCES 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. LINKS Vincenzo Librandi, Table of n, a(n) for n = 2..200 Index entries for linear recurrences with constant coefficients, signature (21,105,-125). FORMULA G.f.: x^2/((1-x)*(1+5*x)*(1-25*x)). a(0)=1, a(1)=21, a(2)=546, a(n) = 21*a(n-1) + 105*a(n-2) - 125*a(n-3). - Harvey P. Dale, Jun 24 2011 MATHEMATICA Table[QBinomial[n, 2, -5], {n, 2, 22}] (* or *) LinearRecurrence[ {21, 105, -125}, {1, 21, 546}, 21] (* Harvey P. Dale, Jun 24 2011 *) PROG (Sage) [gaussian_binomial(n, 2, -5) for n in range(2, 18)] # Zerinvary Lajos, May 27 2009 (MAGMA) I:=[1, 21, 546]; [n le 3 select I[n] else 21*Self(n-1) + 105*Self(n-2) - 125*Self(n-3): n in [1..30]] // Vincenzo Librandi, Oct 27 2012 CROSSREFS Sequence in context: A095655 A221766 A080483 * A034789 A297635 A292062 Adjacent sequences:  A015252 A015253 A015254 * A015256 A015257 A015258 KEYWORD nonn,easy AUTHOR Olivier Gérard, Dec 11 1999 STATUS approved

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Last modified January 21 05:39 EST 2020. Contains 331104 sequences. (Running on oeis4.)