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5.1
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(1)
0451 combinatorics 4th edition Round 5 p1
Source:
5/7/2021
Let
n
n
n
be a positive integer and let
a
n
a_n
a
n
be the number of ways to write
n
n
n
as a sum of positive integers, such that any two summands differ by at least
2
2
2
. Also, let
b
n
b_n
b
n
be the number of ways to write
n
n
n
as a sum of positive integers of the form
5
k
±
1
5k\pm 1
5
k
±
1
,
k
∈
Z
k \in Z
k
∈
Z
. Prove that
a
n
b
n
\frac{a_n}{b_n}
b
n
a
n
is a constant for all positive integers
n
n
n
.
combinatorics
4th edition