The Kind Cat
Reputation
97/100 score
4 52 113
Impact
~454k people reached

• 7 helpful flags
• 1,703 votes cast

 39 Research done by high-school students 30 Digit sequence that is not prime in any base 30 Find five consecutive odd integers such that their sum is $55$. 28 Subtraction when second number is bigger than first number 23 Why isnt there only one way of painting these horses?

### Reputation (38,955)

 +10 In a ring $(A,+, \cdot)$ if $aba = a$ then $bab = b$ and all non zero elements in $A$ are invertible. +10 Graph Theory Proof of Website Clicks +11 When does normal maximal subgroup have prime index? +10 Show that a ring $R$ is a division ring if and only if, for each nonzero $a\in R$, there is a unique element $b\in R$ such that $aba = a$.

### Questions (272)

 44 difference between class, set , family and collection 36 What is category theory useful for? 33 Proof the Fibonacci numbers are not a polynomial. 29 What's a good place to learn Lie groups? 26 if there are 5 points on a sphere then 4 of them belong to a half-sphere.

### Tags (318)

 570 combinatorics × 424 181 discrete-mathematics × 131 418 elementary-number-theory × 194 178 graph-theory × 156 298 abstract-algebra × 189 132 algebra-precalculus × 66 256 group-theory × 160 118 contest-math × 81 191 number-theory × 98 115 probability × 106

### Accounts (14)

 Mathematics 38,955 rep 452113 Puzzling 667 rep 115 MathOverflow 426 rep 613 Stack Overflow 157 rep 9 English Language & Usage 126 rep 114