OFFSET
4,2
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 4..200
FORMULA
G.f.: x^4/((1-x)*(1-6*x)*(1-36*x)*(1-216*x)*(1-1296*x)). - Vincenzo Librandi, Aug 11 2016
a(n) = Product_{i=1..4} (6^(n-i+1)-1)/(6^i-1), by definition. - Vincenzo Librandi, Aug 11 2016
MATHEMATICA
Table[QBinomial[n, 4, 6], {n, 4, 20}] (* Vincenzo Librandi, Aug 11 2016 *)
PROG
(Sage) [gaussian_binomial(n, 4, 6) for n in range(4, 15)] # Zerinvary Lajos, May 27 2009
(Magma) r:=4; q:=6; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..20]]; // Vincenzo Librandi, Aug 11 2016
(PARI) r=4; q=6; for(n=r, 30, print1(prod(j=1, r, (1-q^(n-j+1))/(1-q^j)), ", ")) \\ G. C. Greubel, Jun 07 2018
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
Offset changed by Vincenzo Librandi, Aug 11 2016
STATUS
approved