A383510 Number of integer partitions of n that are neither Look-and-Say nor section-sum.

0, 0, 0, 1, 0, 0, 3, 2, 5, 10, 14, 19, 33, 38, 55, 81, 107, 137, 201, 248, 349, 450, 596, 745, 1000, 1242, 1611, 2007, 2567, 3164, 4025, 4920, 6166, 7545, 9347, 11360, 14004, 16932, 20686, 24949, 30305, 36366, 43939, 52521, 63098, 75221

Offset

0,7

Comments

An integer partition is Look-and-Say iff it is possible to choose a disjoint family of strict partitions, one of each of its multiplicities. These are ranked by A351294.

An integer partition is section-sum iff its conjugate is Look-and-Say, meaning it is possible to choose a disjoint family of strict partitions, one of each of its positive 0-appended differences. These are ranked by A381432.

Links

Table of n, a(n) for n=0..45.

Example

The a(3) = 1 through a(10) = 14 partitions:
  (21)  .  .  (42)    (421)   (431)    (432)     (532)
              (321)   (3211)  (521)    (531)     (541)
              (2211)          (3221)   (621)     (721)
                              (4211)   (3321)    (4321)
                              (32111)  (4221)    (5221)
                                       (4311)    (5311)
                                       (5211)    (6211)
                                       (32211)   (32221)
                                       (42111)   (33211)
                                       (321111)  (42211)
                                                 (43111)
                                                 (52111)
                                                 (421111)
                                                 (3211111)

Mathematica

disjointFamilies[y_]:=Select[Tuples[IntegerPartitions /@ Length/@Split[y]], UnsameQ@@Join@@#&];
conj[y_]:=If[Length[y]==0, y, Table[Length[Select[y, #>=k&]], {k, 1, Max[y]}]];
Table[Length[Select[IntegerPartitions[n], disjointFamilies[#]=={} && disjointFamilies[conj[#]]=={}&]], {n, 0, 15}]

Crossrefs

Ranking sequences are shown in parentheses below.

These partitions are ranked by (A383517).

A000041 counts integer partitions, strict A000009.

A048767 is the Look-and-Say transform, fixed points A048768, counted by A217605.

A239455 counts Look-and-Say partitions (A351294), complement A351293 (A351295).

A239455 counts section-sum partitions (A381432), complement A351293 (A381433).

A336866 counts non Wilf partitions (A130092), conjugate (A383513).

A351592 counts non Wilf Look-and-Say partitions (A384006).

A381431 is the section-sum transform.

A383508 counts partitions that are both Look-and-Say and section-sum (A383515).

A383509 counts partitions that are Look-and-Say but not section-sum (A383516).

A383509 counts partitions that are not Look-and-Say but are section-sum (A384007).

A383519 counts section-sum Wilf partitions (A383520).

A383530 counts partitions that are neither Wilf nor conjugate Wilf (A383531).

Cf. A033461, A047966, A098859, A122111, A320348, A325324, A325325, A383511, A383709.

Sequence in context: A257981 A128914 A050063 * A274761 A100885 A209199

Adjacent sequences: A383507 A383508 A383509 * A383511 A383512 A383513

Keyword

nonn

Author

Gus Wiseman, May 18 2025

Status

approved