OFFSET
0,6
COMMENTS
A composition of n is a finite sequence of positive integers summing to n. These compositions must be strict.
FORMULA
For n > 1, the version where singletons are considered coprime is a(n) + 1.
EXAMPLE
The a(5) = 2 through a(12) = 14 compositions (empty column indicated by dot):
(2,3) . (2,5) (3,5) (2,7) (3,7) (2,9) (5,7)
(3,2) (3,4) (5,3) (4,5) (7,3) (3,8) (7,5)
(4,3) (5,4) (2,3,5) (4,7) (2,3,7)
(5,2) (7,2) (2,5,3) (5,6) (2,7,3)
(3,2,5) (6,5) (3,2,7)
(3,5,2) (7,4) (3,4,5)
(5,2,3) (8,3) (3,5,4)
(5,3,2) (9,2) (3,7,2)
(4,3,5)
(4,5,3)
(5,3,4)
(5,4,3)
(7,2,3)
(7,3,2)
MATHEMATICA
Table[Length[Join@@Permutations/@Select[IntegerPartitions[n], !MemberQ[#, 1]&&CoprimeQ@@#&]], {n, 0, 30}]
CROSSREFS
A022340 intersected with A333227 is a ranking sequence (using standard compositions A066099) for these compositions.
A337450 is the relatively prime instead of pairwise coprime version, with strict case A337451 and unordered version A302698.
A337462 allows 1's, with strict case A337561 (or A101268 with singletons), unordered version A327516 with Heinz numbers A302696, and 3-part case A337461.
A337485 is the unordered version (or A007359 with singletons considered coprime), with Heinz numbers A337984.
A337563 is the case of unordered triples.
KEYWORD
nonn
AUTHOR
Gus Wiseman, Oct 06 2020
STATUS
approved