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Gaussian polynomials (Definition)

For an indeterminate $ q$ and integers $ n \ge m \ge 0$ we define the following:

(a) $ (m)_q = q^{m-1} + q^{m-2} + \cdots + 1$ for $ m>0$,

(b) $ (m!)_q = (m)_q (m-1)_q \cdots (1)_q$ for $ m>0$, and $ (0!)_q = 1$,

(c) $ {n \choose m}_q = \frac{(n!)_q}{(m!)_q ((n-m)!)_q}$. If $ m>n$ then we define $ {n \choose m}_q=0$.

The expressions $ {n \choose m}_q$ are called $ q$-binomial coefficients or Gaussian polynomials.

Note: if we replace $ q$ with 1, then we obtain the familiar integers, factorials, and binomial coefficients. Specifically,

(a) $ (m)_1 = m$,

(b) $ (m!)_1 = m!$,

(c) $ {n \choose m}_1 = {n \choose m}$.

(d) $ {m \choose m}_q=1$.



"Gaussian polynomials" is owned by mathcam. [ full author list (2) | owner history (1) ]
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Other names:  q-binomial coefficients
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Cross-references: binomial coefficients, factorials, coefficients, expressions, integers, indeterminate
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This is version 5 of Gaussian polynomials, born on 2001-10-19, modified 2006-02-18.
Object id is 378, canonical name is GaussianPolynomials.
Accessed 3756 times total.

Classification:
AMS MSC16S36 (Associative rings and algebras :: Rings and algebras arising under various constructions :: Ordinary and skew polynomial rings and semigroup rings)
 05A10 (Combinatorics :: Enumerative combinatorics :: Factorials, binomial coefficients, combinatorial functions)
 05A30 (Combinatorics :: Enumerative combinatorics :: $q$-calculus and related topics)

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