Sphere Online Judge (SPOJ)

ID	NAME	QUALITY	USERS	DIFFICULTY C I
29695	GO GOA GONE	14	510	11 13
10232	Distinct Primes	63	4479	9 9
34670	TWISTED ARRAY	-2	73	3 10
18164	Atoms in the Lab	28	3136	7 5
30829	ARE YOU GOOD IN MATHS?	4	172	12 9
25942	Ball sum	35	1401	11 11
30826	Bernoulli numbers	3	5	23 12
106	Binary Stirling Numbers	2	2096	4 17
328	Bishops	73	7587	14 6
28288	Super Amoeba	9	161	19 17
27380	Painting Hat	5	229	12 13
4453	Bouncing Balls II		210
36671	Bipartite Permutation (Hard)	2	3	26 34
4202	Brackets Parade		221
16102	Can you play carrom !!!	2	207	15 12
13626	Charu and Coin Distribution	7	281	10 20
26607	CODER FIRST PROBLEM	28	945	5 7
21357	Crucial Equation	57	3491	3 10
18295	Problem2	1	51	1 6
18298	Problem5	6	420	13 11
13769	Roommate Agreement	41	1217	11 17
26315	Crazy Smoker	21	1098	4 9
19976	HYPERCUBES	1	98	1 21
291	Cube Root	1	225	26 13
1681	Cylinder	2	888	9 26
1391	Summing to a Square Prime	16	1339	13 17
25725	DB & GCD	1	90	1 17
25741	AMUSING SEQUENCE	1	42	1 50
16211	Boring Factorials	23	1248	12 15
12914	Totient Extreme	28	1267	8 12
3476	Deposit	1	220	9 17
20172	Divisiblity by 3	10	535	13 9
15965	PLAY WITH MATH	52	5461	3 5
5161	Factorial vs Power	13	968	13 14
10293	FANCY NUMBERS	14	1582	7 8
11	Factorial	140	40407	5 12
24	Small factorials	122	32998	15 9
4408	Build a Fence	29	10034	4 5
36563	Hard Fibonacci	4	12	12 17
25067	Fibonacci Polynomial	7	121	12 23
18530	Font Size	4	183	12 3
5978	Frequent Prime Ranges	5	592	13 10
4672	Yanu in Movie theatre	9	1255	1 26
26780	GORDON AND GALLERY	3	74	1 9
26952	Game Of Ones	14	762	5 9
9952	111…1 Squared	8	1608	5 10
4200	Hamster flight	12	1065	5 12
902	Hangover	35	13850	4 3
18202	HUGE GCD	12	493	8 11
31928	Those College Days!	2	205	5 6

We dare not propose a definition ;)

https://en.wikipedia.org/wiki/Mathematics