Элементы дискретной математики. Часть I - 90 стр.

UptoLike

P (x)=
n
k=0
a
k
p
k
(x)
p
0
(x),p
1
(x), ... p
k
(x)
k k 0.
1,x,x
2
, ... [x]
1
, [x]
2
, ...
n 0
x
n
=
n
i=0
S(n, k)[x]
k
. (6)
x
f : A B, |A| = n, |B| =
x.
x
n
.
f f(A).
f A f(A),
Y B, |Y | = k,
f : A B F (A)=Y, s
n,k
,
k!S(n, k). Y k
C(n, k)
x
n
=
x
k=0
C(x, k)k!S(n, k)=
n
k=0
[x]
k
S(n, k)(7)
x n, S(n, k)=0
k>n [x]
k
=0 k<x
x 0,
s(n, k)
x [x]
k
:
[x]
n
=
n
k=0
s(n, k)x
k
. (8)
s(n, k)
S(n, k) [x]
1
, [x]
2
,
x, x
2
, s(n, k)=0 k>n. s(n, k)
s(n, k)=s(n 1,k 1) (n 1)s(n 1,k) 0 <k<n,
s(n, n)=1
n 0,
s(n, n)=0
n>0.