Esteban Crespi
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 Mar3 revised Is $53$ expressible in this form? added 551 characters in body Sep26 revised Infinitely many primes congruent to 1 mod prime The proof was incomplete Sep5 revised Number of pairs $(i, j)$ where $1\leq i < j \leq N$ such that $i|j$ added 148 characters in body Sep5 revised Number of pairs $(i, j)$ where $1\leq i < j \leq N$ such that $i|j$ Improved the image and hopefully the explanation Apr6 revised Comparing sums of surds without any aids added 53 characters in body Mar31 revised Algorithm to find representation of an element of field extension $\mathbb{Q}(q)$ in the form $\sum a_i q^i$ added 125 characters in body Mar16 revised Partial fraction decomposition of p'/p Removed the c Mar14 revised Reducing simultaneously a pair of fractions $\frac{a^2}{b},\frac{ a^3}{c}$ using only gcds EDIT: Changed to make more clear the question. Mar14 revised Reducing simultaneously a pair of fractions $\frac{a^2}{b},\frac{ a^3}{c}$ using only gcds Sorry the method I give is not correct Dec22 revised Generalizing Ramanujan's proof of Bertrand's Postulate: Can Ramanujan's approach be used to show a prime between $4x$ and $5x$ for $x \ge 3$ minor edit Jun21 revised How prove that:$\varphi(2)+\varphi(3)+\varphi(4)+\cdots+\varphi(n)\ge\frac{n(n-1)}{4}+1$ I have rewritten the proof as the original was very confusing and contained some incorrect statements. Jun21 revised How prove that:$\varphi(2)+\varphi(3)+\varphi(4)+\cdots+\varphi(n)\ge\frac{n(n-1)}{4}+1$ deleted 2 characters in body Dec1 revised Galois group and the Quaternion group added 1 characters in body Dec1 revised Galois group and the Quaternion group Added explanation Nov3 revised Half the rationals? Added a generalization Oct15 revised Tiling a minimal perimeter region with $n$ unit squares Sketch of proof Apr19 revised Burgess on quadratic residues and non-residues edited body Apr19 revised Burgess on quadratic residues and non-residues added 1406 characters in body Apr17 revised Burgess on quadratic residues and non-residues correction Feb21 revised Is it a bad idea to use a Sieve of Eratosthenes to find all primes up to very large N? added 1962 characters in body