140]
RESEARCHES ON THE PARTITION OF NUMBERS.
245
(S+l)
which leads to
P'(0, 1, 2 ... k) m ^ (km —a) =
S s i(—V coeff. x& k ~ s)m in t
( (1 - X 2 ) ... (1 -tf s )(l -#)(1 -X 2 ) ... (1
where the summation extends, as in the former case, from s = 0 to the greatest value
of s, for which (£& — s)m — |a-^s(s + 1) is positive or zero, or, if we please, when k is
even, from 5 = 0 to s = \k—l, and when s is odd, from 5 = 0 to s = \ (k -1). The
condition, in order that the fraction may be a proper one for all values of s, is.
when k is even, a+l <\k(k+ 2), and when k is odd, a + 1 < \(k + 1) (k + 3).
To transform the preceding expressions, I write when k is odd x 2 instead of x,
and I put for shortness 6 instead of %k-s or 2(\k-s), and y instead of §a + ^s(5 + l)
or a + 5(s + l); we have to consider an expression of the form
coefficient x 6m in
xy
Tx'
where Fx is the product of factors of the form 1 - x a . Suppose that a is the least
common multiple of a and 6, then (1 - x a ') = (1 - x a ) is an integral function of x,
equal x x suppose, and 1 -f- (1 — x a ) = x x + (1 - & a ')- Making this change in all the
factors of Fx which require it (i.e. in all the factors except those in which a is a
multiple of 6), the general term becomes
coefficient x 6m in
x y Hx
~Gx
where Gx is a product of factors of the form 1 — x M ', in which a' is a multiple of 0,
i.e. Gx is a rational and integral function of x 9 . But in the numerator x y lix we may
reject, as not contributing to the formation of the coefficient of x 9m , all the terms in
which the indices are not multiples of 0; the numerator is thus reduced to a rational
and integral function of x e , and the general term is therefore of the form
coefficient x 6m in
\(x e )
k^Y
or what is the same thing, of the form
coefficient x m in
\x
KX
where kx is the product of factors of the form 1 — x a , and Xx is a rational and integral
function of x. The particular value of the fraction depends on the value of 5; and
uniting the different terms, vve have an expression
coefficient x m in S s (—) s
which is equivalent to
coefficient x m in
d>x
fx ’