A326842 Number of integer partitions of n whose parts all divide n and whose length also divides n.

1, 1, 2, 2, 3, 2, 5, 2, 5, 3, 5, 2, 21, 2, 5, 6, 9, 2, 22, 2, 21, 6, 5, 2, 134, 3, 5, 6, 23, 2, 157, 2, 27, 6, 5, 6, 478, 2, 5, 6, 208, 2, 224, 2, 31, 63, 5, 2, 1720, 3, 30, 6, 34, 2, 322, 6, 295, 6, 5, 2, 13899, 2, 5, 68, 126, 8, 429, 2, 42, 6, 358, 2, 19959, 2

Offset

0,3

Comments

The Heinz numbers of these partitions are given by A326847.

Links

Fausto A. C. Cariboni, Table of n, a(n) for n = 0..419

Example

The a(1) = 1 through a(8) = 5 partitions:
  (1)  (2)   (3)    (4)     (5)      (6)       (7)        (8)
       (11)  (111)  (22)    (11111)  (33)      (1111111)  (44)
                    (1111)           (222)                (2222)
                                     (321)                (4211)
                                     (111111)             (11111111)
The a(12) = 21 partitions:
  (12)
  (6,6)
  (4,4,4)
  (6,3,3)
  (6,4,2)
  (3,3,3,3)
  (4,3,3,2)
  (4,4,2,2)
  (4,4,3,1)
  (6,2,2,2)
  (6,3,2,1)
  (6,4,1,1)
  (2,2,2,2,2,2)
  (3,2,2,2,2,1)
  (3,3,2,2,1,1)
  (3,3,3,1,1,1)
  (4,2,2,2,1,1)
  (4,3,2,1,1,1)
  (4,4,1,1,1,1)
  (6,2,1,1,1,1)
  (1,1,1,1,1,1,1,1,1,1,1,1)

Mathematica

Table[Length[Select[IntegerPartitions[n, All, Divisors[n]], Divisible[n, Length[#]]&]], {n, 1, 30}]

Crossrefs

Partitions using divisors are A018818.

Partitions whose length divides their sum are A067538.

Cf. A047993, A102627, A316413, A326841, A326843, A326847.

Sequence in context: A180125 A342086 A272209 * A326843 A323347 A322900

Adjacent sequences: A326839 A326840 A326841 * A326843 A326844 A326845

Keyword

nonn

Author

Gus Wiseman, Jul 26 2019

Status

approved