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2024 India STEMS
STEMS 2024 Math Cat B
P5
find all functions satisfying p | f(f(x)) − x^2
find all functions satisfying p | f(f(x)) − x^2
Source: STEMS 2024, CAT B, P5
December 17, 2023
function
algebra
Problem Statement
Find the sum of all primes
p
<
50
p < 50
p
<
50
, for which there exists a function
f
:
{
0
,
…
,
p
−
1
}
→
{
0
,
…
,
p
−
1
}
f \colon \{0, \ldots , p -1\} \rightarrow \{0, \ldots , p -1\}
f
:
{
0
,
…
,
p
−
1
}
→
{
0
,
…
,
p
−
1
}
such that
p
∣
f
(
f
(
x
)
)
−
x
2
p \mid f(f(x)) - x^2
p
∣
f
(
f
(
x
))
−
x
2
.
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