A325687 - OEIS

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A325687

Triangle read by rows where T(n,k) is the number of length-k compositions of n such that every distinct consecutive subsequence has a different sum.

1, 1, 1, 1, 2, 1, 1, 3, 0, 1, 1, 4, 4, 0, 1, 1, 5, 5, 0, 0, 1, 1, 6, 12, 4, 0, 0, 1, 1, 7, 12, 5, 0, 0, 0, 1, 1, 8, 25, 8, 4, 0, 0, 0, 1, 1, 9, 24, 12, 3, 0, 0, 0, 0, 1, 1, 10, 40, 32, 8, 4, 0, 0, 0, 0, 1, 1, 11, 41, 41, 6, 3, 0, 0, 0, 0, 0, 1

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OFFSET

1,5

COMMENTS

A composition of n is a finite sequence of positive integers summing to n.

LINKS

Table of n, a(n) for n=1..78.

EXAMPLE

The distinct consecutive subsequences of (1,1,3,3) are (1), (1,1), (3), (1,3), (1,1,3), (3,3), (1,3,3), (1,1,3,3), all of which have different sums, so (1,1,3,3) is counted under a(8).

Triangle begins:

1 1

1 2 1

1 3 0 1

1 4 4 0 1

1 5 5 0 0 1

1 6 12 4 0 0 1

1 7 12 5 0 0 0 1

1 8 25 8 4 0 0 0 1

1 9 24 12 3 0 0 0 0 1

1 10 40 32 8 4 0 0 0 0 1

1 11 41 41 6 3 0 0 0 0 0 1

1 12 60 76 14 4 4 0 0 0 0 0 1

1 13 60 88 16 6 3 0 0 0 0 0 0 1

Row n = 8 counts the following compositions:

(8) (17) (116) (1115) (11111111)

(26) (125) (1133)

(35) (143) (2222)

(44) (152) (3311)

(53) (215) (5111)

(62) (233)

(71) (251)

(332)

(341)

(512)

(521)

(611)

MATHEMATICA

Table[Length[Select[Join@@Permutations/@IntegerPartitions[n, {k}], UnsameQ@@Total/@Union[ReplaceList[#, {___, s__, ___}:>{s}]]&]], {n, 15}, {k, n}]

CROSSREFS

Row sums are A325676.

Column k = 2 is A000027.

Column k = 3 is A325688.

Cf. A000079, A007318, A048004, A108917, A143823, A169942, A266223, A325592, A325680, A325685.

Sequence in context: A290691 A366900 A155726 * A230079 A105400 A194516

Adjacent sequences: A325684 A325685 A325686 * A325688 A325689 A325690

KEYWORD

nonn,tabl

AUTHOR

Gus Wiseman, May 13 2019

STATUS

approved