HP 39gII

Sequence app 127
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Sequence app
About the Sequence app
The Sequence app allows you to explore sequences.
You can define a sequence named, for example, U1:
• in terms of n
• in terms of U1(n–1)
•in terms of U1(n–2)
• in terms of another sequence, for example, U2(n)
• in any combination of the above.
The Sequence app allows you to create two types of
graphs:
– A Stairsteps graph plots n on the horizontal
axis and U
n
on the vertical axis.
– A Cobweb graph plots U
n–1
on the horizontal
axis and U
n
on the vertical axis.
Getting started with the Sequence app
The following example defines and then plots an
expression in the Sequence app. The sequence illustrated
is the well-known Fibonacci sequence where each term,
from the third term on, is the sum of the preceding two
terms. In this example, we specify three sequence fields:
the first term, the second term and a rule for generating
all subsequent terms.
However, you can also define a sequence by specifying
just the first term and the rule for generating all
subsequent terms. You will, though, have to enter the
second term if the HP 39gII is unable to calculate it
automatically. Typically if the nth term in the sequence
depends on n–2, then you must enter the second term.