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Show that if four distinct integers are chosen between $1$ and $60$ inclusive, some two of them must differ by at most $19$

Finding a formula to sum natural numbers up to $n$ [duplicate]

Show that this structure is an affinely regular polygon

How many three digit numbers are not divisible by 3, 5 or 11?

If $n\ge2$, Prove $\binom{2n}{3}$ is even.

Why am I under-counting when calculating the probability of a full house?

Probability of getting all four answers right, with true and false in each question

combinatorial answer using inclusion exclusion principles

How to prove $\left \lceil \frac{n}{m} \right \rceil = \left \lfloor \frac{n+m-1}{m} \right \rfloor$?

Is L(K4) graph planar?

finding big omega of $n^k$ by splitting the sum (big-$O$ notation)

Is there a formula for finding the number of nonisomorphic simple graphs that have n nodes?

Find All Solutions to System of Congruence

Probability of a random graph being triangle-free

Prove that for every positive integer $n$, $1/1^2+1/2^2+1/3^2+\cdots+1/n^2\le2-1/n$

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Prove $1+\frac{1}{\sqrt{2}}+\frac{1}{\sqrt{3}}+\dots+\frac{1}{\sqrt{n}} > 2\:(\sqrt{n+1} − 1)$

Show that if four distinct integers are chosen between $1$ and $60$ inclusive, some two of them must differ by at most $19$

Finding a formula to sum natural numbers up to $n$ [duplicate]

Show that this structure is an affinely regular polygon

How many three digit numbers are not divisible by 3, 5 or 11?

If $n\ge2$, Prove $\binom{2n}{3}$ is even.

Why am I under-counting when calculating the probability of a full house?

Probability of getting all four answers right, with true and false in each question

combinatorial answer using inclusion exclusion principles

How to prove $\left \lceil \frac{n}{m} \right \rceil = \left \lfloor \frac{n+m-1}{m} \right \rfloor$?

Is L(K4) graph planar?

finding big omega of $n^k$ by splitting the sum (big-$O$ notation)

Is there a formula for finding the number of nonisomorphic simple graphs that have n nodes?

Find All Solutions to System of Congruence

Probability of a random graph being triangle-free

Prove that for every positive integer $n$, $1/1^2+1/2^2+1/3^2+\cdots+1/n^2\le2-1/n$