A195153 Irregular triangle read by rows in which row n lists numbers d-1 that do not divide n, where d divides n.

2, 3, 4, 5, 6, 3, 7, 2, 8, 4, 9, 10, 5, 11, 12, 6, 13, 2, 4, 14, 3, 7, 15, 16, 5, 8, 17, 18, 3, 9, 19, 2, 6, 20, 10, 21, 22, 5, 7, 11, 23, 4, 24, 12, 25, 2, 8, 26, 3, 6, 13, 27, 28, 4, 9, 14, 29, 30, 3, 7, 15, 31, 2, 10, 32, 16, 33, 4, 6, 34, 5, 8, 11, 17, 35

Offset: 3

Author

Omar E. Pol, Sep 19 2011

Keywords

• nonn
• tabf

Comments

It appears that only rows 3, 4, 6, 8, 12, 24 have the property that all their members are primes. See the example. See also the comment at A018253.

Examples

			Written as an irregular triangle:
2,
3,
4,
5,
6,
3, 7,
2, 8,
4, 9,
10,
5, 11,
12,
6, 13,
2, 4, 14,
3, 7, 15,
16,
5, 8, 17,
18,
3, 9, 19,
2, 6, 20,
10, 21,
22,
5, 7, 11, 23
		

Links

• T. D. Noe, Rows n = 3..1000, flattened

Crossrefs

Cf. A018253, A027750, A173540, A195150.

Programs

Mathematica

Flatten[Table[d = Divisors[n]; Select[Rest[d-1], Mod[n, #] > 0 &], {n, 3 , 100}]] (* T. D. Noe, Sep 23 2011 *)