Math, Angle, and Test Operations 2-21
nPr
(number of permutations) returns the number of
permutations of
items
taken
number
at a time.
items
and
number
must be nonnegative integers. Both
items
and
number
can be lists.
items
nPr
number
nCr
(number of combinations) returns the number of
combinations of
items
taken
number
at a time.
items
and
number
must be nonnegative integers. Both
items
and
number
can be lists.
items
nCr
number
!
(factorial) returns the factorial of either an integer or a
multiple of .5. For a list, it returns factorials for each
integer or multiple of .5.
value
must be
‚L
.5 and
69.
value
!
Note: The factorial is computed recursively using the relationship
(n+1)! = n
ä
n!, until n is reduced to either 0 or
L
1/2. At that point, the
definition 0!=1 or the definition (
L
1
à
2)!=
‡p
is used to complete the
calculation. Hence:
n!=n
ä
(n
N
1)
ä
(n
N
2)
ä
...
ä
2
ä
1, if n is an integer
‚
0
n!= n
ä
(n
N
1)
ä
(n
N
2)
ä
...
ä
1
à
2
ä
‡p
, if n+1
à
2 is an integer
‚
0
n! is an error, if neither n nor n+1
à
2 is an integer
‚
0.
(The variable n equals
value
in the syntax description above.)
nPr,
nCr
! (Factorial)
