A316245 Number of ways to split an integer partition of n into consecutive subsequences with weakly decreasing sums.

1, 1, 3, 6, 14, 25, 52, 89, 167, 279, 486, 786, 1322, 2069, 3326, 5128, 8004, 12055, 18384, 27203, 40588, 59186, 86645, 124583, 179784, 255111, 362767, 509319, 715422, 993681, 1380793, 1899630, 2613064, 3564177, 4857631, 6572314, 8884973, 11930363, 16002853

Offset

0,3

Links

Andrew Howroyd, Table of n, a(n) for n = 0..50

Gus Wiseman, The a(5) = 25 split partitions.

Gus Wiseman, The a(6) = 52 split partitions.

Example

The a(4) = 14 split partitions:
  (4)
  (31)
  (22)
  (211)
  (3)(1)
  (2)(2)
  (1111)
  (21)(1)
  (2)(11)
  (111)(1)
  (11)(11)
  (2)(1)(1)
  (11)(1)(1)
  (1)(1)(1)(1)

Mathematica

comps[q_]:=Table[Table[Take[q, {Total[Take[c, i-1]]+1, Total[Take[c, i]]}], {i, Length[c]}], {c, Join@@Permutations/@IntegerPartitions[Length[q]]}];
Table[Sum[Length[Select[comps[y], OrderedQ[Total/@#, GreaterEqual]&]], {y, IntegerPartitions[n]}], {n, 10}]

Prog

(PARI) a(n)={my(recurse(r, m, s, t, f)=if(m==0, r==0, if(f, self()(r, min(m, t), t, 0, 0)) + self()(r, m-1, s, t, 0) + if(t+m<=s, self()(r-m, min(m, r-m), s, t+m, 1)))); recurse(n, n, n, 0, 0)} \\ Andrew Howroyd, Jan 18 2024

Crossrefs

Cf. A000041, A001970, A063834, A316223, A317546, A319001, A319003.

Cf. A317508, A317715, A318434, A318683, A318684, A319794.

Sequence in context: A291988 A285460 A236429 * A002219 A006906 A324703

Adjacent sequences: A316242 A316243 A316244 * A316246 A316247 A316248

Keyword

nonn

Author

Gus Wiseman, Sep 29 2018

Extensions

a(21) onwards from Andrew Howroyd, Jan 18 2024

Status

approved