%I M5404 #44 Jul 14 2023 14:40:36
%S 1,156,20306,2558556,320327931,40053706056,5007031143556,
%T 625886840206056,78236053707784181,9779511680526143556,
%U 1222439084242108174806,152804888634672088643556,19100611156944225555440431,2387576396558283557830831056
%N Gaussian binomial coefficient [ n,3 ] for q = 5.
%D 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.
%D I. P. Goulden and D. M. Jackson, Combinatorial Enumeration. Wiley, NY, 1983, p. 99.
%D N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
%D M. Sved, Gaussians and binomials, Ars. Combinatoria, 17A (1984), 325-351.
%H Vincenzo Librandi, <a href="/A006112/b006112.txt">Table of n, a(n) for n = 3..200</a>
%H Simon Plouffe, <a href="https://arxiv.org/abs/0911.4975">Approximations de séries génératrices et quelques conjectures</a>, Dissertation, Université du Québec à Montréal, 1992; arXiv:0911.4975 [math.NT], 2009.
%H Simon Plouffe, <a href="/A000051/a000051_2.pdf">1031 Generating Functions</a>, Appendix to Thesis, Montreal, 1992
%H M. Sved, <a href="/A006095/a006095.pdf">Gaussians and binomials</a>, Ars. Combinatoria, 17A (1984), 325-351. (Annotated scanned copy)
%H <a href="/index/Rec#order_04">Index entries for linear recurrences with constant coefficients</a>, signature (156, -4030, 19500, -15625).
%F G.f.: x^3/((1-x)*(1-5*x)*(1-25*x)*(1-125*x)). - _Vincenzo Librandi_, Aug 07 2016
%F a(n) = Product_{i=1..3} (5^(n-i+1)-1)/(5^i-1), by definition. - _Vincenzo Librandi_, Aug 07 2016
%F a(n) = (5^n-1)*(5^n-5)*(5^n-25)/1488000. - _Robert Israel_, Feb 01 2018
%p A006112:=1/(z-1)/(125*z-1)/(25*z-1)/(5*z-1); # [conjectured by _Simon Plouffe_ in his 1992 dissertation]
%p seq((5^n-1)*(5^n-5)*(5^n-25)/1488000, n=3..30); # _Robert Israel_, Feb 01 2018
%t Table[QBinomial[n, 3, 5], {n, 3, 20}] (* _Vincenzo Librandi_, Aug 07 2016 *)
%o (Sage) [gaussian_binomial(n,3,5) for n in range(3,14)] # _Zerinvary Lajos_, May 27 2009
%o (Magma) r:=3; q:=5; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..20]]; // _Vincenzo Librandi_, Aug 07 2016
%K nonn,easy
%O 3,2
%A _N. J. A. Sloane_