A100881 Number of partitions of n in which the sequence of frequencies of the summands is decreasing.

1, 1, 2, 2, 3, 3, 4, 4, 6, 5, 7, 8, 8, 9, 13, 10, 13, 15, 16, 18, 21, 17, 24, 28, 26, 26, 36, 32, 38, 42, 40, 46, 52, 48, 63, 63, 59, 63, 85, 77, 81, 92, 89, 102, 116, 98, 122, 134, 130, 140, 157, 145, 165, 182, 190, 191, 207, 195, 235, 259, 232, 252, 293, 279

Offset

0,3

Links

Alois P. Heinz, Table of n, a(n) for n = 0..1000

Example

a(7) = 4 because in each of the four partitions [7], [3,3,1], [2,2,2,1], [1,1,1,1,1,1,1] the frequency with which a summand is used decreases as the summand decreases.

Maple

b:= proc(n, i, t) option remember;
      if n<0 then 0
    elif n=0 then 1
    elif i=0 then 0
    else      b(n, i-1, t)
         +add(b(n-i*j, i-1, j), j=1..min(t-1, floor(n/i)))
      fi
    end:
a:= n-> b(n, n, n+1):
seq(a(n), n=0..60);  # Alois P. Heinz, Feb 21 2011

Mathematica

b[n_, i_, t_] := b[n, i, t] = Which[n<0, 0, n==0, 1, i==0, 0, True, b[n, i-1, t] + Sum[b[n-i*j, i-1, j], {j, 1, Min[t-1, Floor[n/i]]}]]; a[n_] := b[n, n, n+1]; Table[a[n], {n, 0, 60}] (* Jean-François Alcover, Jul 15 2015, after Alois P. Heinz *)

Prog

(Haskell)
a100881 = p 0 0 1 where
   p m m' k x | x == 0    = if m > m' || m == 0 then 1 else 0
              | x < k     = 0
              | m == 0    = p 1 m' k (x - k) + p 0 m' (k + 1) x
              | otherwise = p (m + 1) m' k (x - k) +
                            if m > m' then p 0 m (k + 1) x else 0
-- Reinhard Zumkeller, Dec 27 2012

Crossrefs

Cf. A100882, A100883, A100884.

Cf. A100471, A098859.

Sequence in context: A325691 A326668 A198318 * A053263 A317908 A056039

Adjacent sequences: A100878 A100879 A100880 * A100882 A100883 A100884

Keyword

nonn

Author

David S. Newman, Nov 21 2004

Extensions

More terms from Alois P. Heinz, Feb 21 2011

Status

approved