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DLMF: §26.3 Lattice Paths: Binomial Coefficients ‣ Properties ‣ Chapter 26 Combinatorial Analysis
§26.3 Lattice Paths: Binomial Coefficients
Contents
§26.3(i) Definitions
§26.3(ii) Generating Functions
§26.3(iii) Recurrence Relations
§26.3(iv) Identities
§26.3(v) Limiting Form
§26.3(i) Definitions
( m n ) is the number of ways of choosing n objects from a collection
of m distinct objects without regard to order. ( m + n n ) is the
number of lattice paths from ( 0 , 0 ) to ( m , n ) . See also 1.2(i) .
The number of lattice paths from ( 0 , 0 ) to ( m , n ) , m ≤ n , that stay on
or above the line y = x is ( m + n m ) − ( m + n m − 1 ) .
26.3.1
( m n ) = ( m m − n ) = m ! ( m − n ) ! n ! ,
m ≥ n ,
For numerical values of ( m n ) and ( m + n n ) see Tables
26.3.1 and 26.3.2 .
Table 26.3.1: Binomial coefficients ( m n ) .
Table 26.3.2: Binomial coefficients ( m + n m ) for lattice paths.
§26.3(ii) Generating Functions
26.3.3
∑ n = 0 m ( m n ) x n = ( 1 + x ) m ,
m = 0 , 1 , … ,
26.3.4
∑ m = 0 ∞ ( m + n m ) x m = 1 ( 1 − x ) n + 1 ,
| x | < 1 .
§26.3(iii) Recurrence Relations
26.3.5
( m n )
= ( m − 1 n ) + ( m − 1 n − 1 ) ,
m ≥ n ≥ 1 ,
26.3.6
( m n )
= m n ( m − 1 n − 1 ) = m − n + 1 n ( m n − 1 ) ,
m ≥ n ≥ 1 ,
26.3.7
( m + 1 n + 1 ) = ∑ k = n m ( k n ) ,
m ≥ n ≥ 0 ,
26.3.8
( m n ) = ∑ k = 0 n ( m − n − 1 + k k ) ,
m ≥ n ≥ 0 .
§26.3(iv) Identities
26.3.10
( m n ) = ∑ k = 0 n ( − 1 ) n − k ( m + 1 k ) ,
m ≥ n ≥ 0 ,
26.3.11
( 2 n n ) = 2 n ( 2 n − 1 ) ( 2 n − 3 ) ⋯ 3 ⋅ 1 n ! .
See also §1.2(i) .
§26.3(v) Limiting Form
26.3.12
( 2 n n ) ∼ 4 n π n ,
n → ∞ .