Operation Manual

Chapter 6: Sequence Graphing 109
You can enter the function name from the keyboard (y [u], y [v], y [w]) or use the shortcut menu
t a.
Generally, sequences are either nonrecursive or recursive. Sequences are evaluated only at consecutive
integer values. n is always a series of consecutive integers, starting at zero or any positive integer.
Nonrecursive Sequences
In a nonrecursive sequence, the nth term is a function of the independent variable n. Each term is
independent of all other terms.
For example, in the nonrecursive sequence below, you can calculate
u(5) directly, without first
calculating u(1) or any previous term.
The sequence equation above returns the sequence 2, 4, 6, 8, 10, … for n = 1, 2, 3, 4, 5, … .
Note: You may leave blank the initial value
u(nMin) when calculating nonrecursive sequences.
Recursive Sequences
In a recursive sequence, the nth term in the sequence is defined in relation to the previous term or the
term that precedes the previous term, represented by u(nN1) and u(nN2). A recursive sequence may also
be defined in relation to
n, as in u(n)=u(nN1)+n.
For example, in the sequence below you cannot calculate u(5) without first calculating u(1), u(2), u(3),
and
u(4).
Using an initial value
u(nMin) = 1, the sequence above returns 1, 2, 4, 8, 16, ... .
You must type each character of the terms. For example, to enter
u(nN1), press y [u] £ „ ¹ À
¤.
Note: The Sequence function u can also be entered using the Y-VA R S shortcut menu t a.
Recursive sequences require an initial value or values, since they reference undefined terms.