#271 · Combinatorics
Onto functions from {1,…,5} to {1,2,3}
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#272 · Functions
Solutions of f(f(x)) = x for f(x) = x² − 2
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#273 · Calculus
Series ∑ n²/2ⁿ
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#274 · Arithmetic
Largest n such that (n + 10) divides n³ + 100
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#275 · Algebra
x⁴ + y⁴ + z⁴ from elementary symmetric polynomials
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#276 · Combinatorics
10-digit binary strings with no two consecutive 1s
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#277 · Calculus
Series ∑ k/2^k
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#278 · Algebra
Sum of integers n with |n² − 10n| < 5
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#279 · Combinatorics
5-element subsets of {1, …, 20} with no two consecutive elements
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#280 · Arithmetic
GCD of 1! + 2! + … + 10! and 10!
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#281 · Functions
Real solutions of x² = 2^x
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#282 · Combinatorics
Non-negative 4-tuples summing to 10 with a + b ≥ 3
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#283 · Arithmetic
(1⁵ + 2⁵ + … + 100⁵) mod 4
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#284 · Arithmetic
(∑_{k=1}^{100} k · k!) mod 100
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#285 · Arithmetic
Sum of n where n² + 3n + 5 is a prime dividing n² + 1
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#286 · Equations
Ordered pairs (x, y) with 1/x + 1/y = 1/12
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#287 · Arithmetic
Sum of n ≤ 1000 with φ(n) = n/2
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#288 · Combinatorics
Positive integer solutions of x + 2y + 3z = 30
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#289 · Calculus
Series ∑ k(k+1)/2^k
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#290 · Combinatorics
Tiling a 1 × 6 strip with red, blue, and white tiles
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#291 · Algebra
Maximum of x²y³z given x + y + z = 1
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#292 · Arithmetic
Largest prime factor of 101,010,101
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#293 · Combinatorics
Vandermonde sum C(10,0)² + C(10,1)² + … + C(10,10)²
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#294 · Combinatorics
Lattice paths from (0,0) to (10,10) passing through (5,5)
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#295 · Arithmetic
Product of 4 consecutive integers – largest guaranteed divisor
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#296 · Arithmetic
Wieferich primes up to 20
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#297 · Calculus
Maximum area of rectangle inscribed in right triangle with legs 3 and 4
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#298 · Arithmetic
Primes appearing in twin prime pairs up to 100
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