

A341673


Irregular triangle read by rows giving the strictly superior divisors of n.


31



2, 3, 4, 5, 3, 6, 7, 4, 8, 9, 5, 10, 11, 4, 6, 12, 13, 7, 14, 5, 15, 8, 16, 17, 6, 9, 18, 19, 5, 10, 20, 7, 21, 11, 22, 23, 6, 8, 12, 24, 25, 13, 26, 9, 27, 7, 14, 28, 29, 6, 10, 15, 30, 31, 8, 16, 32, 11, 33, 17, 34, 7, 35, 9, 12, 18, 36, 37, 19, 38, 13, 39
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OFFSET

1,1


COMMENTS

We define a divisor dn to be strictly superior if d > n/d. Strictly superior divisors are counted by A056924.


LINKS



EXAMPLE

Row n = 18 lists the strictly superior divisors of 18, which are 6, 9, 18.
Triangle begins:
1: {}
2: 2
3: 3
4: 4
5: 5
6: 3,6
7: 7
8: 4,8
9: 9
10: 5,10
11: 11
12: 4,6,12
13: 13
14: 7,14
15: 5,15
16: 8,16
17: 17
18: 6,9,18
19: 19
20: 5,10,20


MATHEMATICA

Table[Select[Divisors[n], #>n/#&], {n, 100}]


CROSSREFS

Final terms in each row (except n = 1) are A000027.
Row lengths are A056924 (number of strictly superior divisors).
Initial terms in each row are A140271.
The weakly inferior version is A161906.
The weakly superior version is A161908.
The odd terms in each row are counted by A341594.
The squarefree terms in each row are counted by A341595.
The prime terms in each row are counted by A341642.
The strictly inferior version is A341674.
A038548 counts superior (or inferior) divisors.
 Superior: A033677, A051283, A059172, A063538, A063539, A070038, A072500, A116882, A116883, A341591, A341592, A341593, A341675, A341676.


KEYWORD

nonn,tabf


AUTHOR



STATUS

approved



