OFFSET
0,4
COMMENTS
A composition of n is a finite sequence of positive integers with sum n.
EXAMPLE
The a(0) = 1 through a(5) = 13 compositions:
() (1) (2) (3) (4) (5)
(1,2) (1,3) (1,4)
(2,1) (3,1) (2,3)
(1,1,2) (3,2)
(1,2,1) (4,1)
(2,1,1) (1,1,3)
(1,2,2)
(1,3,1)
(2,1,2)
(2,2,1)
(3,1,1)
(1,1,2,1)
(1,2,1,1)
MATHEMATICA
normQ[m_]:=Or[m=={}, Union[m]==Range[Max[m]]];
Table[Length[Select[Join@@Permutations/@IntegerPartitions[n], normQ[Length/@Split[#]]&]], {n, 0, 10}]
CROSSREFS
KEYWORD
nonn
AUTHOR
Gus Wiseman, Nov 20 2019
EXTENSIONS
a(21)-a(26) from Giovanni Resta, Nov 22 2019
a(27)-a(35) from Alois P. Heinz, Jul 06 2020
STATUS
approved