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A022220 Gaussian binomial coefficients [ n,2 ] for q = 6. 2
1, 43, 1591, 57535, 2072815, 74630671, 2686760143, 96723701071, 3482055254095, 125354001240655, 4512744117222991, 162458788655384143, 5848516394205967951, 210546590207087679055, 7579677247549193442895, 272868380912335185925711 (list; graph; refs; listen; history; text; internal format)
OFFSET

2,2

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 2..200

FORMULA

G.f.: x^2/((1-x)*(1-6*x)*(1-36*x)).

a(n) = Product_{i=1..2} (6^(n-i+1)-1)/(6^i-1), by definition. - Vincenzo Librandi, Aug 16 2016

MATHEMATICA

Table[QBinomial[n, 2, 6], {n, 2, 20}] (* Vincenzo Librandi, Aug 10 2016 *)

PROG

(Sage) [gaussian_binomial(n, 2, 6) for n in xrange(2, 17)] # Zerinvary Lajos, May 28 2009

(MAGMA) r:=2; q:=6; [&*[(1-q^(n-i+1))/(1-q^i): i in [1..r]]: n in [r..20]]; // Vincenzo Librandi, Aug 10 2016

(PARI) r=2; 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

Sequence in context: A122575 A014938 A235646 * A297028 A198206 A162881

Adjacent sequences:  A022217 A022218 A022219 * A022221 A022222 A022223

KEYWORD

nonn,easy

AUTHOR

N. J. A. Sloane

EXTENSIONS

Offset changed by Vincenzo Librandi, Aug 10 2016

STATUS

approved

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Last modified March 19 11:10 EDT 2019. Contains 321329 sequences. (Running on oeis4.)