A098859 Number of partitions of n into parts each of which is used a different number of times.

1, 1, 2, 2, 4, 5, 7, 10, 13, 15, 21, 28, 31, 45, 55, 62, 82, 105, 116, 153, 172, 208, 251, 312, 341, 431, 492, 588, 676, 826, 905, 1120, 1249, 1475, 1676, 2003, 2187, 2625, 2922, 3409, 3810, 4481, 4910, 5792, 6382, 7407, 8186, 9527, 10434

Offset

0,3

Comments

Fill, Janson and Ward refer to these partitions as Wilf partitions. - Peter Luschny, Jun 04 2012

Links

Simon Langowski and Mark Daniel Ward, Table of n, a(n) for n = 0..2000 (terms 0..300 from M. D. Ward, 301..700 from Maciej Ireneusz Wilczynski)

James Allen Fill, Svante Janson and Mark Daniel Ward, Partitions with Distinct Multiplicities of Parts: On An "Unsolved Problem" Posed By Herbert S. Wilf, The Electronic Journal of Combinatorics, Volume 19, Issue 2 (2012)

Daniel Kane and Robert C. Rhoades, Asymptotics for Wilf's partitions with distinct multiplicities

Martin Klazar, What is an answer? — remarks, results and problems on PIO formulas in combinatorial enumeration, part I, arXiv:1808.08449 [math.CO], 2018.

Simon Langowski, Program to compute Wilf Partitions, 2018

Stephan Wagner, The Number of Fixed Points of Wilf's Partition Involution, The Electronic Journal of Combinatorics, 20(4) (2013), #P13.

Doron Zeilberger, Using generatingfunctionology to enumerate distinct-multiplicity partitions; Local copy/a> [Pdf file only, no active links]

Formula

log(a(n)) ~ N*log(N) where N = (6*n)^(1/3) (see Fill, Janson and Ward). - Peter Luschny, Jun 04 2012

Example

a(6)=7 because 6= 4+1+1= 3+3= 3+1+1+1= 2+2+2= 2+1+1+1+1= 1+1+1+1+1+1. Four unrestricted partitions of 6 are not counted by a(6): 5+1, 4+2, 3+2+1 because at least two different summands are each used once; 2+2+1+1 because each summand is used twice.
From Gus Wiseman, Apr 19 2019: (Start)
The a(1) = 1 through a(9) = 15 partitions are the following. The Heinz numbers of these partitions are given by A130091.
  1   2    3     4      5       6        7         8          9
      11   111   22     221     33       322       44         333
                 211    311     222      331       332        441
                 1111   2111    411      511       422        522
                        11111   3111     2221      611        711
                                21111    4111      2222       3222
                                111111   22111     5111       6111
                                         31111     22211      22221
                                         211111    41111      33111
                                         1111111   221111     51111
                                                   311111     411111
                                                   2111111    2211111
                                                   11111111   3111111
                                                              21111111
                                                              111111111
(End)

Mathematica

a[n_] := Length[sp = Split /@ IntegerPartitions[n]] - Count[sp, {___List, b_List, ___List, c_List, ___List} /; Length[b] == Length[c]]; Table[a[n], {n, 0, 48}] (* Jean-François Alcover, Jan 17 2013 *)

Prog

(Haskell)
a098859 = p 0 [] 1 where
   p m ms _      0 = if m `elem` ms then 0 else 1
   p m ms k x
     | x < k       = 0
     | m == 0      = p 1 ms k (x - k) + p 0 ms (k + 1) x
     | m `elem` ms = p (m + 1) ms k (x - k)
     | otherwise   = p (m + 1) ms k (x - k) + p 0 (m : ms) (k + 1) x
-- Reinhard Zumkeller, Dec 27 2012
(PARI) a(n)={((r, k, b, w)->if(!k||!r, if(r, 0, 1), sum(m=0, r\k, if(!m || !bittest(b, m), self()(r-k*m, k-1, bitor(b, 1<<m), w+m)))))(n, n, 1, 0)} \\ Andrew Howroyd, Aug 31 2019

Crossrefs

Row sums of A182485.

Cf. A100471, A100881, A105637, A211858, A211859, A211860, A211861, A211862, A211863, A242882.

Cf. A047966 (each part appears the same number of times), A090858, A116608, A130091, A325242.

Sequence in context: A286948 A211863 A333190 * A364345 A239455 A362610

Adjacent sequences: A098856 A098857 A098858 * A098860 A098861 A098862

Keyword

nonn,nice

Author

David S. Newman, Oct 11 2004

Extensions

Corrected and extended by Vladeta Jovovic, Oct 22 2004

Status

approved