| Summary: | In this study, we seek to find relations between the number of representations of a
nonnegative integer n as a sum of figurate numbers of different types.
Firstly, we give a relation between the number of representations, ck(n), of n as
the sum k cubes and the number of representations, pk(n), of n as the sum of k
triangular pyramidal numbers, namely under certain conditions
pk(n) = c k odd (v);
where c k odd denotes the number of representations as a sum of k odd cubes and the
integer v is derived from n. Then we extend this problem by considering sums of
s-th powers with s > 3 and the associated polytopic numbers of order s.
Next, we discuss the relation between ɸ(2;k)(n), the number of representations of
n as a sum of k fourth powers, and ψ(2;k)(n), the number of representations of n as a sum of k terms of the form 8γ2 + 2γ where γ is a triangular number. When
1 ≤ k ≤ 7, the relation is
ɸ(2;k)(8n + k) = 2kψ (2;k) (n).
We extend this result by considering the relation between the number of represen-
tations of n as a sum of k 2m-th powers and the number of representations of n as
a sum of k terms determined by an associated polynomial of degree m evaluated
at a triangular number.
Thirdly, we consider the relation between sk(n), the number of representations of
n as a sum of k squares, and ek(n), the number of representations of n as a sum
of k centred pentagonal numbers. When 1 ≤k ≤ 7, this relation is
αkek(n) = sk (8n -3k)÷5 ; where αk = 2k + 2k-1 (k4)
We extend the analysis to the number of representations induced by a partition γ
of k into m parts. If corresponding number of representations of n are respectively
sγ(n) and eγ(n), then
βγeγ(n) = sγ(8n - 3k)÷5
where
βγ = 2m + 2(m-1) (( i1/4) + (i1/2)(i2/1)+(i1/1)(i3/1)
and ij denotes the number of parts of γ which are equal to j.
We end this thesis with a short discussion and proposal of various open problems
for further research.
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