A191973 Irregular triangle read by rows: row n consists of n and the positive integers m where m-n divides m*n.

1, 2, 1, 2, 3, 4, 6, 2, 3, 4, 6, 12, 2, 3, 4, 5, 6, 8, 12, 20, 4, 5, 6, 10, 30, 2, 3, 4, 5, 6, 7, 8, 9, 10, 12, 15, 18, 24, 42, 6, 7, 8, 14, 56, 4, 6, 7, 8, 9, 10, 12, 16, 24, 40, 72, 6, 8, 9, 10, 12, 18, 36, 90, 5, 6, 8, 9, 10, 11, 12, 14, 15, 20, 30, 35, 60

Offset

1,2

Comments

The maximum term of the n-th row is n*(n+1). The minimum term of the n-th row seems to be A063428(n) if n>=2. The length of row n is A146564(n) + 1.

Links

Nathaniel Johnston, Rows 1..250, flattened

Example

The triangle begins:
1 2
1 2 3 4  6
2 3 4 6  12
2 3 4 5  6  8  12 20
4 5 6 10 30
2 3 4 5  6  7  8  9  10 12 15 18 24 42
6 7 8 14 56
...

Maple

for n from 1 to 10 do for m from 1 to n*(n+1) do if(n=m or m*n mod (m-n) = 0)then printf("%d, ", m): fi: od: od:

Crossrefs

Cf. A162821 (row 30), A162822 (row 36), A162823 (row 42), A162824 (row 48), A162825 (row 60), A127730.

Sequence in context: A220237 A050040 A277282 * A290973 A173497 A022875

Adjacent sequences: A191970 A191971 A191972 * A191974 A191975 A191976

Keyword

nonn,easy,tabf

Author

Nathaniel Johnston, Jun 22 2011

Status

approved