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Answers
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90
Should the formula for the inverse of a 2x2 matrix be obvious?
67
Checkmate in $\omega$ moves? (3)
47
Contest problems with connections to deeper mathematics. (4)
43
How good is Kamenetsky’s formula for the number of digits in n-factorial?
39
Alternating sum of square roots of binomial coefficients
37
Is there a “classical” proof of this $j$-value congruence?
36
Irreversible chess (3)
36
Does $(x^2 - 1)(y^2 - 1) = c z^4$ have a rational point, with z non-zero, for any given rational c?
36
the following inequality is true，but I can’t prove it (2)
31
How to decide this function takes integer values?
29
Is there any sequence $a_n$ of nonnegative numbers for which $\sum_{n \geq 1}a_n^2 <\infty$ and $\sum_{n \geq 1}\left(\sum_{k \geq 1}\frac{a_{kn}}{k}\right)^2=\infty$?
29
cube + cube + cube = cube
28
A 14th and 26th-power Dedekind eta function identity?
26
Is there anything special about the Riemann surface $y^2 = x(x^{10}+11x^5-1)$?
26
Matrix inequality $(A-B)^2 \leq c (A+B)^2$ ?
26
Heuristically false conjectures
26
Jumping in the integers
25
Which Diophantine equations can be solved using continued fractions?
22
Sum of squares modulo a prime
21
Are nontrivial integer solutions known for $x^3+y^3+z^3=3$?
21
Truncated Exponential Series Modulo $p$: Deeper meaning for a Putnam Question. (2)
20
The divisor bound in number fields
20
Negative values of Riemann zeta function on the critical line.
19
Sum of trigonometric functions (2)
19
Three consecutive quadratic residues problem
19
A quadratic form represents all primes except for the primes 2 and 11.
19
The function $\sum_{0}^{\infty} x^n/n^n$
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Combinatorial interpretation of ${i\choose n}$, where $i^2=-1$
18
Exponential sums over finite fields with even characteristic
18
Number fields with same discriminant and regulator?
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