A239484 Number of (4,0)-separable partitions of n; see Comments.

0, 1, 1, 2, 1, 2, 3, 4, 5, 6, 7, 9, 11, 13, 15, 19, 22, 26, 31, 36, 42, 51, 58, 68, 79, 92, 107, 125, 143, 165, 191, 221, 253, 293, 333, 383, 440, 503, 574, 657, 747, 853, 971, 1105, 1253, 1427, 1616, 1833, 2076, 2349, 2655, 3006, 3389, 3826, 4313, 4861

Offset

5,4

Comments

Suppose that p is a partition of n into 2 or more parts and that h is a part of p. Then p is (h,0)-separable if there is an ordering x, h, x, h, ..., h, x of the parts of p, where each x represents any part of p except h. Here, the number of h's on the ends of the ordering is 0. Similarly, p is (h,1)-separable if there is an ordering x, h, x, h, ..., x, h, where the number of h's on the ends is 1; next, p is (h,2)-separable if there is an ordering h, x, h, ..., x, h. Finally, p is h-separable if it is (h,i)-separable for i = 0,1,2.

Links

Table of n, a(n) for n=5..60.

Example

The (4,0)-separable partitions of 12 are 741, 642, 543, 24141, so that a(12) = 4.

Mathematica

z = 65; -1 + Table[Count[IntegerPartitions[n], p_ /; 2 Count[p, 1] == Length[p] - 1], {n, 2, z}]  (* A165652 *)
-1 + Table[Count[IntegerPartitions[n], p_ /; 2 Count[p, 2] == Length[p] - 1], {n, 3, z}]  (* A239482 *)
-1 + Table[Count[IntegerPartitions[n], p_ /; 2 Count[p, 3] == Length[p] - 1], {n, 4, z}]  (* A239483 *)
-1 + Table[Count[IntegerPartitions[n], p_ /; 2 Count[p, 4] == Length[p] - 1], {n, 5, z}]  (* A239484 *)
-1 + Table[Count[IntegerPartitions[n], p_ /; 2 Count[p, 5] == Length[p] - 1], {n, 6, z}] (* A239485 *)

Crossrefs

Cf. A239467, A165652, A239482, A239483, A239485.

Sequence in context: A369900 A137846 A080915 * A058714 A057045 A237753

Adjacent sequences: A239481 A239482 A239483 * A239485 A239486 A239487

Keyword

nonn,easy

Author

Clark Kimberling, Mar 20 2014

Status

approved