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A325545 Number of compositions of n with distinct differences. 28
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 (list; graph; refs; listen; history; text; internal format)
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).

LINKS

Table of n, a(n) for n=0..39.

Gus Wiseman, Sequences counting and ranking integer partitions by the differences of their successive parts.

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}]

CROSSREFS

Cf. A000079, A000740, A008965, A059966, A070211, A175342, A242882, A325325, A325352, A325546, A325547, A325548, A325551, A325554.

Sequence in context: A278697 A129941 A287147 * A159079 A068947 A068948

Adjacent sequences:  A325542 A325543 A325544 * A325546 A325547 A325548

KEYWORD

nonn

AUTHOR

Gus Wiseman, May 10 2019

EXTENSIONS

More terms from Alois P. Heinz, May 11 2019

STATUS

approved

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Last modified February 25 19:44 EST 2020. Contains 332257 sequences. (Running on oeis4.)