The function
is
well-poised if
It is very well-poised if it is well-poised and
.
The special case
is
-balanced if
is a nonpositive integer and
When
the function is said to be balanced or
Saalschützian.
The function
with argument unity and general values of the
parameters is discussed in Bühring (1992). Special cases are as
follows:
when
,
. See
Erdélyi et al. (1953a, §4.4(4)) for a non-terminating balanced identity.
when
, or when the series terminates with
:
where
.
when
, or when the series terminates with
.
when
or when
is an integer.
This is (16.4.7) in the case
:

when
, or when the series terminates with
.

when
. The last condition is equivalent to the sum of the top
parameters plus 2 equals the sum of the bottom parameters, that is,
the series is 2-balanced.
when
and
. The function
is analytic in the parameters
when its series expansion converges and the bottom parameters are not negative
integers or zero. (16.4.11) provides a partial analytic continuation
to the region when the only restrictions on the parameters are
, and
, and
. A detailed
treatment of analytic continuation in (16.4.11) and asymptotic
approximations as the variables
approach infinity is given by
Aomoto (1987).
There are two types of three-term identities for
’s. The first
are recurrence relations that extend those for
’s; see
§15.5(ii). Examples are (16.3.7) with
. Also,
and
Methods of deriving such identities are given by Bailey (1964),
Rainville (1960), Raynal (1979), and
Wilson (1978). Lists are given by Raynal (1979) and
Wilson (1978). See Raynal (1979) for a statement in terms
of
symbols (Chapter 34). Also see Wilf and Zeilberger (1992a, b) for information on the Wilf–Zeilberger algorithm which can be
used to find such relations.
The other three-term relations are extensions of Kummer’s relations for
’s given in §15.10(ii). See
Bailey (1964, pp. 19–22).
Balanced
series have transformation formulas and
three-term relations. The basic transformation is given by
when
. These series contain
symbols as special cases
when the parameters are integers; compare §34.4.
The characterizing properties (18.22.2), (18.22.10), (18.22.19), (18.22.20), and (18.26.14) of the Hahn and Wilson class polynomials are examples of the contiguous relations mentioned in the previous three paragraphs.
Contiguous balanced series have parameters shifted by an integer but still balanced. One example of such a three-term relation is the recurrence relation (18.26.16) for Racah polynomials. See Raynal (1979), Wilson (1978), and Bailey (1964).
A different type of transformation is that of Whipple:
when the series on the right terminates and the series on the left converges. When the series on the right does not terminate, a second term appears. See Bailey (1964, §4.4(4)).
For continued fractions for ratios of
functions with argument
unity, see Cuyt et al. (2008, pp. 315–317).
Denote, formally, the bilateral hypergeometric function
Then
This is Dougall’s bilateral sum; see Andrews et al. (1999, §2.8).