|
|
A282748
|
|
Triangle read by rows: T(n,k) is the number of compositions of n into k parts x_1, x_2, ..., x_k such that gcd(x_i, x_j) = 1 for all i != j (where 1 <= k <= n).
|
|
3
|
|
|
1, 1, 1, 1, 2, 1, 1, 2, 3, 1, 1, 4, 3, 4, 1, 1, 2, 9, 4, 5, 1, 1, 6, 3, 16, 5, 6, 1, 1, 4, 15, 4, 25, 6, 7, 1, 1, 6, 9, 28, 5, 36, 7, 8, 1, 1, 4, 21, 16, 45, 6, 49, 8, 9, 1, 1, 10, 9, 52, 25, 66, 7, 64, 9, 10, 1, 1, 4, 39, 16, 105, 36, 91, 8, 81, 10, 11, 1, 1, 12, 9, 100, 25, 186, 49, 120, 9, 100, 11, 12, 1, 1, 6, 45, 16, 205, 36, 301, 64, 153, 10, 121, 12, 13, 1
(list;
table;
graph;
refs;
listen;
history;
text;
internal format)
|
|
|
OFFSET
|
1,5
|
|
COMMENTS
|
See A101391 for the triangle T(n,k) = number of compositions of n into k parts x_1, x_2, ..., x_k such that gcd(x_1,x_2,...,x_k) = 1 (2 <= k <= n).
|
|
LINKS
|
|
|
FORMULA
|
It seems that no general formula or recurrence is known, although Shonhiwa gives formulas for a few of the early diagonals.
|
|
EXAMPLE
|
Triangle begins:
1;
1, 1;
1, 2, 1;
1, 2, 3, 1;
1, 4, 3, 4, 1;
1, 2, 9, 4, 5, 1;
1, 6, 3, 16, 5, 6, 1;
1, 4, 15, 4, 25, 6, 7, 1;
1, 6, 9, 28, 5, 36, 7, 8, 1;
1, 4, 21, 16, 45, 6, 49, 8, 9, 1;
1, 10, 9, 52, 25, 66, 7, 64, 9, 10, 1;
1, 4, 39, 16, 105, 36, 91, 8, 81, 10, 11, 1;
1, 12, 9, 100, 25, 186, 49, 120, 9, 100, 11, 12, 1;
...
Row n = 6 counts the following compositions:
(6) (15) (114) (1113) (11112) (111111)
(51) (123) (1131) (11121)
(132) (1311) (11211)
(141) (3111) (12111)
(213) (21111)
(231)
(312)
(321)
(411)
(End)
|
|
MATHEMATICA
|
Table[Length[Select[Join@@Permutations/@IntegerPartitions[n, {k}], Length[#]==1||CoprimeQ@@#&]], {n, 10}, {k, n}] (* Gus Wiseman, Nov 12 2020 *)
|
|
CROSSREFS
|
A072704 counts the unimodal instead of coprime version.
A101391 is the relatively prime instead of pairwise coprime version.
A000740 counts relatively prime compositions, with strict case A332004.
A007360 counts pairwise coprime or singleton strict partitions.
A051424 counts pairwise coprime or singleton partitions, ranked by A302569.
A097805 counts compositions by sum and length.
A178472 counts compositions with a common divisor.
A305713 counts pairwise coprime strict partitions.
A335235 ranks pairwise coprime or singleton compositions.
A337562 counts pairwise coprime or singleton strict compositions.
A337665 counts compositions whose distinct parts are pairwise coprime, ranked by A333228.
|
|
KEYWORD
|
|
|
AUTHOR
|
|
|
STATUS
|
approved
|
|
|
|