An arithmetic sequence
is a sequence whose consecutive terms differ
by the same real number, called the common difference.
The general term of an arithmetic sequence a1,
a2, a3, ... an,
with common difference d is an
= a1 +
(n - 1)d.
A geometric sequence is
a sequence whose consecutive terms have the same quotient,
called the common ratio. The general
term of a geometric sequence g1,
g2, g3, ... gn,
with common ratio r is gn = g1rn-1.
A Fibonacci-type sequence
is a sequence in which the general term is given
by the formula s1 = sn-1
+ sn-2 where s1
and s2 are given. The
Fibonacci sequence is that sequence
for which s1 = s2 =