A356236 Number of integer partitions of n with a neighborless part.

0, 1, 2, 2, 4, 4, 8, 9, 16, 20, 31, 40, 59, 76, 105, 138, 184, 238, 311, 400, 515, 656, 831, 1052, 1322, 1659, 2064, 2572, 3182, 3934, 4837, 5942, 7264, 8872, 10789, 13109, 15865, 19174, 23105, 27796, 33361, 39956, 47766, 56985, 67871, 80675, 95750, 113416

Offset: 0

Author

Gus Wiseman, Aug 24 2022

Keywords

• nonn

Comments

A part x of a partition is neighborless if neither x - 1 nor x + 1 are parts.

Examples

			The a(1) = 1 through a(8) = 9 partitions:
  (1)  (2)   (3)    (4)     (5)      (6)       (7)
       (11)  (111)  (22)    (41)     (33)      (52)
                    (31)    (311)    (42)      (61)
                    (1111)  (11111)  (51)      (331)
                                     (222)     (421)
                                     (411)     (511)
                                     (3111)    (4111)
                                     (111111)  (31111)
                                               (1111111)
		

Crossrefs

The complement is counted by A355394, singleton case A355393.

The singleton case is A356235, ranked by A356237.

The strict case is A356607, complement A356606.

These partitions are ranked by the complement of A356736.

A000041 counts integer partitions, strict A000009.

A000837 counts relatively prime partitions, ranked by A289509.

A007690 counts partitions with no singletons, complement A183558.

Cf. A066205, A112798, A319630, A325160, A328171, A328172, A328187, A328221.

Programs

Mathematica

Table[Length[Select[IntegerPartitions[n],Function[ptn,Or@@Table[!MemberQ[ptn,x-1]&&!MemberQ[ptn,x+1],{x,Union[ptn]}]]]],{n,0,30}]

Formula

a(n) = A000041(n) - A355394(n).