A239243 - OEIS

A239243

Number of partitions of n into distinct parts for which (number of odd parts) >= (number of even parts).

1, 1, 0, 2, 1, 3, 2, 4, 4, 6, 7, 8, 11, 11, 17, 16, 25, 22, 36, 31, 49, 44, 68, 61, 90, 85, 120, 118, 156, 160, 204, 217, 261, 291, 337, 386, 429, 507, 548, 662, 694, 854, 882, 1096, 1112, 1396, 1406, 1765, 1768, 2219, 2223, 2776, 2784, 3451, 3484, 4275

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OFFSET

0,4

COMMENTS

a(n) = Sum_{k>=0} A240021(n,k). - Alois P. Heinz, Apr 02 2014

LINKS

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

FORMULA

a(n) + A239239(n) = A000009(n) for n >=1.

EXAMPLE

a(8) = 4 counts these partitions: 71, 53, 521, 431.

MAPLE

b:= proc(n, i, t) option remember; `if`(n>i*(i+1)/2, 0,

`if`(n=0, `if`(t>=0, 1, 0 ), b(n, i-1, t)+`if`(i>n, 0,

b(n-i, i-1, t+`if`(irem(i, 2)=1, 1, -1)))))

end:

a:= n-> b(n$2, 0):

seq(a(n), n=0..60); # Alois P. Heinz, Mar 15 2014

MATHEMATICA

z = 55; p[n_] := p[n] = IntegerPartitions[n]; d[u_] := d[u] = DeleteDuplicates[u]; g[u_] := g[u] = Length[u];

Table[g[Select[Select[p[n], d[#] == # &], Count[#, _?OddQ] < Count[#, _?EvenQ] &]], {n, 0, z}] (* A239239 *)

Table[g[Select[Select[p[n], d[#] == # &], Count[#, _?OddQ] <= Count[#, _?EvenQ] &]], {n, 0, z}] (* A239240 *)

Table[g[Select[Select[p[n], d[#] == # &], Count[#, _?OddQ] == Count[#, _?EvenQ] &]], {n, 0, z}] (* A239241 *)

Table[g[Select[Select[p[n], d[#] == # &], Count[#, _?OddQ] > Count[#, _?EvenQ] &]], {n, 0, z}] (* A239242 *)

Table[g[Select[Select[p[n], d[#] == # &], Count[#, _?OddQ] >= Count[#, _?EvenQ] &]], {n, 0, z}] (* A239243 *)

(* Peter J. C. Moses, Mar 10 2014 *)

b[n_, i_, t_] := b[n, i, t] = If[n>i*(i+1)/2, 0, If[n==0, If[t>=0, 1, 0], b[n, i-1, t]+If[i>n, 0, b[n-i, i-1, t+If[Mod[i, 2]==1, 1, -1]]]]]; a[n_] := b[n, n, 0]; Table[a[n], {n, 0, 60}] (* Jean-François Alcover, Aug 30 2016, after Alois P. Heinz *)

CROSSREFS

Cf. A239239, A239240, A239241, A239242, A000009.

Sequence in context: A116928 A239948 A034391 * A206738 A282971 A174618

Adjacent sequences: A239240 A239241 A239242 * A239244 A239245 A239246

KEYWORD

nonn,easy

AUTHOR

Clark Kimberling, Mar 13 2014

STATUS

approved