A096749 Number of partitions of n into distinct parts, the least being 2.

0, 0, 1, 0, 0, 1, 1, 1, 1, 2, 2, 3, 3, 4, 5, 6, 7, 9, 10, 12, 15, 17, 20, 24, 28, 32, 38, 44, 51, 59, 68, 78, 91, 103, 118, 136, 155, 176, 201, 228, 259, 294, 332, 375, 425, 478, 538, 607, 681, 764, 858, 961, 1075, 1203, 1343, 1499, 1673, 1863, 2073, 2308, 2564, 2847, 3161, 3504

Offset

0,10

Comments

The old entry with this sequence number was a duplicate of A071569.

a(n), n>2 is the Euler transform of [0,0,1,1,1] joined with period [0,1]. - Georg Fischer, Aug 15 2020

Links

Alois P. Heinz, Table of n, a(n) for n = 0..5000

Formula

G.f.: x^2*Product_{j>=3} (1+x^j). - R. J. Mathar, Jul 31 2008

a(n) = A025148(n-2), n>1. - R. J. Mathar, Sep 30 2008

G.f.: Sum_{k>=1} x^(k*(k + 3)/2) / Product_{j=1..k-1} (1 - x^j). - Ilya Gutkovskiy, Nov 24 2020

Maple

b:= proc(n, i) option remember;
      `if`(n=0, 1, `if`((i-2)*(i+3)/2<n, 0,
       add(b(n-i*j, i-1), j=0..min(1, n/i))))
    end:
a:= n-> `if`(n<2, 0, b(n-2$2)):
seq(a(n), n=0..60);  # Alois P. Heinz, Feb 07 2014
# Using the function EULER from Transforms (see link at the bottom of the page).
[0, 0, 1, op(EULER([0, 0, 1, 1, seq(irem(n, 2), n=1..57)]))]; # Peter Luschny, Aug 19 2020

Mathematica

b[n_, i_] := b[n, i] = If[n == 0, 1, If[(i-2)*(i+3)/2<n, 0, Sum[b[n-i*j, i-1], {j, 0, Min[1, n/i]}]]]; a[n_] := If[n<2, 0, b[n-2, n-2]]; Table[a[n], {n, 0, 60}] (* Jean-François Alcover, Oct 13 2014, after Alois P. Heinz *)
Join[{0}, Table[Count[Last /@ Select[IntegerPartitions@n, DeleteDuplicates[#] == # &], 2], {n, 66}]] (* Robert Price, Jun 13 2020 *)

Crossrefs

Cf. A025147, A071569.

Cf. A096765 (least=1), A022824 (3), A022825 (4), A022826 (5), A022827 (6), A022828 (7), A022829 (8), A022830 (9), A022831 (10).

Sequence in context: A335766 A026823 A025148 * A036821 A237980 A026798

Adjacent sequences: A096746 A096747 A096748 * A096750 A096751 A096752

Keyword

nonn

Author

N. J. A. Sloane, Sep 28 2008

Status

approved