HP 39gs

T
T
h
h
e
e
‘
‘
L
L
o
o
o
o
p
p
’
’
g
g
r
r
o
o
u
u
p
p
o
o
f
f
f
f
u
u
n
n
c
c
t
t
i
i
o
o
n
n
s
s
This is a group of functions that may be of use for students studying
discrete functions and sequences but are primarily of use to
programmers.
ITERATE(<expression>,<var_name>,<num>,<num>)
This function evaluates an expression in terms of a variable, starting with a supplied initial value, for a
specified number of iterations. Each iteration uses the answer to the previous evaluation as the value for the
variable in the next evaluation.
Eg.
ITERATE(X
2
- 1, X, 2, 5) gives an answer of 15745023
This answer is obtained as follows:
initial value: X=2 first iteration using supplied
x
2
−
1 = 3 initial value of 2.
new value: X=3 second iteration
2
1x
−
= 8
new value X=8 third iteration
x
2
−
1 = 63
new value X=63 fourth iteration
2
1x
−
= 3968
new value fifth iteration
2
1x
−
= 15745023
Final answer: X = 15 745 023
X=3968
193