A number which cannot be written as a⋅b + b⋅c + c⋅a, for 0<a<b<c. more
The known idoneal numbers are :
1,
2,
3,
4,
5,
6,
7,
8,
9,
10,
12,
13,
15,
16,
18,
21,
22,
24,
25,
28,
30,
33,
37,
40,
42,
45,
48,
57,
58,
60,
70,
72,
78,
85,
88,
93,
102,
105,
112,
120,
130,
133,
165,
168,
177,
190,
210,
232,
240,
253,
273,
280,
312,
330,
345,
357,
385,
408,
462,
520,
760,
840,
1320,
1365,
1848.
Distribution of the remainders when the numbers in this family are divided by n=2, 3,..., 11. (I took into account 65 values, from 1 to 1848).
n\r | 0 | 1 |
2 | 40 | 25 | 2 |
3 | 37 | 25 | 3 | 3 |
4 | 24 | 22 | 16 | 3 | 4 |
5 | 26 | 4 | 15 | 17 | 3 | 5 |
6 | 22 | 9 | 2 | 15 | 16 | 1 | 6 |
7 | 18 | 12 | 13 | 4 | 11 | 4 | 3 | 7 |
8 | 20 | 10 | 8 | 1 | 4 | 12 | 8 | 2 | 8 |
9 | 4 | 7 | 1 | 17 | 9 | 1 | 16 | 9 | 1 | 9 |
10 | 16 | 2 | 10 | 7 | 2 | 10 | 2 | 5 | 10 | 1 | 10 |
11 | 10 | 11 | 5 | 7 | 8 | 6 | 4 | 3 | 3 | 5 | 3 |
A pictorial representation of the table above
Imagine to divide the members of this family by a number n and compute the remainders. Should they be uniformly distributed, each remainder from 0 to n-1 would be obtained in about (1/n)-th of the cases. This outcome is represented by a white square. Reddish (resp. bluish) squares represent remainders which appear more (resp. less) frequently than 1/n.