OFFSET
1,3
COMMENTS
The signature of a multiset is a partition consisting of the repetition factors of the original partition. Regarding a partition as a multiset, the signature of a partition is defined. E.g., [1,1,3,4,4] = [1^2,3^1,4^2], so the repetition factors are 2,1,2, making the signature [1,2,2] = [1,2^2]. Partitions are written here in increasing part size, so [1,2^2] is 1,2,2, not 2,2,1. - Edited by Franklin T. Adams-Watters, Jul 09 2012
The sum (or order) of the signature is the number of parts of the original partition and the number of parts of the signature is the number of distinct parts of the original partition.
LINKS
Robert Price, Table of n, a(n) for n = 1..8266 (first 20 rows).
M. Abramowitz and I. A. Stegun, eds., Handbook of Mathematical Functions, National Bureau of Standards, Applied Math. Series 55, Tenth Printing, 1972 [alternative scanned copy].
EXAMPLE
[1];
[1], [2];
[1], [1,1], [3];
[1], [1,1], [2], [1,2], [4];
...
From Hartmut F. W. Hoft, Apr 25 2015: (Start)
Extending the triangle to rows 5 and 6 where row headings indicate the number of elements in the underlying partitions. Brackets group the multiplicities of a single partition.
row 5 row 6
1: [1] [1]
2: [1,1] [1,1] [1,1] [1,1] [2]
3: [1,2] [1,2] [1,2] [1,1,1] [3]
4: [1,3] [1,3] [2,2]
5: [5] [1,4]
6: [6]
(End)
MATHEMATICA
(* row[] and triangle[] compute structured rows of the triangle as laid out above *)
mL[pL_] := Map[Last[Transpose[Tally[#]]]&, pL]
row[n_] := Map[Map[Sort, mL[#]]&, GatherBy[Map[Sort, IntegerPartitions[n]], Length]]
triangle[n_] := Map[row, Range[n]]
a115621[n_]:= Flatten[triangle[n]]
Take[a115621[8], 105] (* data *) (* Hartmut F. W. Hoft, Apr 25 2015 *)
Map[Sort[#, Less] &, Table[Last /@ Transpose /@ Tally /@ Sort[Reverse /@ IntegerPartitions[n]], {n, 8}], 2]
PROG
(SageMath) from collections import Counter
def A115621_row(n):
h = lambda p: sorted(Counter(p).values())
return flatten([h(p) for k in (0..n) for p in Partitions(n, length=k)])
for n in (1..10): print(A115621_row(n)) # Peter Luschny, Nov 02 2019
CROSSREFS
KEYWORD
nonn,tabf
AUTHOR
Franklin T. Adams-Watters, Jan 25 2006
STATUS
approved