1. Introduction and Motivation
Given an indeterminate and an
integer , the
rising factorial is defined by Following Bailey [1], the classical hypergeometric series
reads as For , the series converges only when the
real part of the sum of the numerator parameters is less that of the
denominator parameters.
There exist numerous summation formulae of hypergeometric series in
the literature (see for example [2, 3, 4, 5 6 7, 8]).
By means of the algebro–geoemtric approach,
Asakura–Otsubo–Terasoma [9] examined following exotic (1)-series and proved, when and
the following elegant formulae: By employing the integral representations, the
authors [10]
succeeded in not only reviewing the above identities, but also
evaluating further series for and .
Moreover, Chen K-W [11]
and the authors [12]
extended these results to the following series by introducing five extra
integer parameters provided
that and such that the series is
well–defined and convergent.
Recall that for the nonterminating -series, there are two
fundamental transformations named after Thomae and Kummer (cf. [1] and Page 98)
where denotes the parameter
excess. The objective of this paper is to investigate the following four
classes of (1)-series
represented by the respective examples (in the right column): where and such that
the series are not only well–defined and nonterminating, but also
convergent and irreducible to known -series.
Their evaluations will be fulfilled by making use of Kummer and
Thomae transformations in conjunction with the closed formulae for the
series 2 obtained in [12] via the linearization method
(cf. [13, 14]).
The remaining part of the paper will be divided into four sections,
dedicated separately to evaluations of the afore described four classes
of (1)-series (A), (B), (C)
and (D).
2. Evaluation of the
(1)-Series in Class (A)
Performing the parameter replacements in Thomae transformation 3 we can state the
resulting equation as the transformation formula below.
This formula is valid for two variables and five integer parameters subject to conditions
, , and such that both series are
not only well–defined and convergent, but also nonterminating and
irreducible to known -series.
Observe that the (1)-series
on the right-hand side of Theorem 1 has the same
parameter structure as the exotic (1)-series displayed in 2. By applying the summation formulae
obtained in [10, 12], we can further evaluate,
in closed form, the following (1)-series in class (A), specified
by and .
3. Evaluation of the
(1)-Series in Class (B)
Alternatively, under the parameter settings Thomae transformation
3 becomes the following one.
In order that the above two -series are not only well–defined
and convergent, but also nonterminating and irreducible to known -series, the two variables and five integer parameters should satisfy the
conditions , , and . Evaluating the exotic
(1)-series on the right-hand
side of Theorem 2 by the summation formulae shown in [10, 12], we find
the following identities for the (1)-series in class (B), specified
by and .
4. Evaluation of the
(1)-Series in Class (C)
Performing the parameter replacements in Kummer transformation 4 with we can state the
resulting equation as the transformation formula below.
The above formula is valid for two variables and five integer parameters subject to conditions
, , and such that both series are
not only well–defined and convergent, but also nonterminating and
irreducible to known -series. Since the (1)-series on the right-hand side of
Theorem 3 can be evaluated by the summation
formulae given in [10, 12], we derive further closed
formulae below for exotic (1)-series in class (C) with the two
variables being specified by and .
5. Evaluation of the
(1)-Series in Class (D)
Finally, under the parameter replacements the transformation
corresponding to Kummer’s 4 is given by the theorem below.
In order that the above two series are not only well–defined and
convergent, but also nonterminating and irreducible to known -series, the following conditions
, , and should be imposed on the two
variables and five integer
parameters . By
employing the summation formulae in [10, 12], we establish further
identities below for the exotic (1)-series in class (D) with and .