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A325545
Number of compositions of n with distinct differences.
55
1, 1, 2, 3, 7, 13, 17, 34, 59, 105, 166, 279, 442, 730, 1157, 1927, 3045, 4741, 7527, 11667, 18048, 27928, 43334, 65861, 101385, 153404, 232287, 347643, 523721, 780083, 1165331, 1725966, 2561625, 3773838, 5561577, 8151209, 11920717, 17364461, 25269939, 36635775
OFFSET
0,3
COMMENTS
A composition of n is a finite sequence of positive integers summing to n.
The differences of a sequence are defined as if the sequence were increasing, so for example the differences of (3,1,2) are (-2,1).
EXAMPLE
The a(1) = 1 through a(6) = 17 compositions:
(1) (2) (3) (4) (5) (6)
(11) (12) (13) (14) (15)
(21) (22) (23) (24)
(31) (32) (33)
(112) (41) (42)
(121) (113) (51)
(211) (122) (114)
(131) (132)
(212) (141)
(221) (213)
(311) (231)
(1121) (312)
(1211) (411)
(1131)
(1221)
(1311)
(2112)
MATHEMATICA
Table[Length[Select[Join@@Permutations/@IntegerPartitions[n], UnsameQ@@Differences[#]&]], {n, 0, 15}]
KEYWORD
nonn
AUTHOR
Gus Wiseman, May 10 2019
EXTENSIONS
More terms from Alois P. Heinz, May 11 2019
STATUS
approved