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URL: https://oeis.org/A025150

⇱ A025150 - OEIS

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A025150
Number of partitions of n into distinct parts >= 5.
5
1, 0, 0, 0, 0, 1, 1, 1, 1, 1, 1, 2, 2, 3, 3, 4, 4, 5, 6, 7, 8, 10, 11, 13, 15, 17, 20, 23, 26, 30, 35, 39, 45, 51, 58, 66, 75, 84, 96, 108, 122, 137, 155, 173, 195, 219, 245, 274, 307, 342, 383, 427, 475, 529, 589, 654, 727, 807, 894, 991, 1098, 1214, 1343, 1485, 1638, 1809, 1995
OFFSET
0,12
LINKS
Kevin Beanland and Hung Viet Chu, On Schreier-type Sets, Partitions, and Compositions, arXiv:2311.01926 [math.CO], 2023.
FORMULA
G.f.: Product_{j>=5} (1+x^j). - Emeric Deutsch, Apr 17 2006
a(n) = A026825(n+4). - R. J. Mathar, Jul 31 2008
a(n) ~ exp(Pi*sqrt(n/3)) / (64*3^(1/4)*n^(3/4)). - Vaclav Kotesovec, Oct 30 2015
G.f.: Sum_{k>=0} x^(k*(k + 9)/2) / Product_{j=1..k} (1 - x^j). - Ilya Gutkovskiy, Nov 24 2020
EXAMPLE
a(12) = 2 because we have [12] and [7,5].
MAPLE
g:=product(1+x^j, j=5..70)-1: gser:=series(g, x=0, 60): seq(coeff(gser, x, n), n=1..53); # Emeric Deutsch, Apr 17 2006
# Alternative:
b:= proc(n, i) option remember;
`if`(n=0, 1, `if`((i-4)*(i+5)/2<n, 0,
add(b(n-i*j, i-1), j=0..min(1, n/i))))
end:
a:= n-> b(n$2):
seq(a(n), n=0..100); # Alois P. Heinz, Feb 07 2014
MATHEMATICA
d[n_] := Select[IntegerPartitions[n], Max[Length /@ Split@#] == 1 && Min[#] >= 5 &]; Table[d[n], {n, 16}] (* strict partitions, parts >= 5 *)
Table[Length[d[n]], {n, 40}] (* A025150 for n >= 1 *)
(* Clark Kimberling, Mar 07 2014 *)
b[n_, i_] := b[n, i] = If[n==0, 1, If[(i-4)*(i+5)/2<n, 0, Sum[b[n-i*j, i-1], {j, 0, Min[1, n/i]}]]]; a[n_] := b[n, n]; Table[a[n], {n, 0, 100}] (* Jean-François Alcover, Oct 22 2015, after Alois P. Heinz *)
nmax = 100; CoefficientList[Series[Product[1+x^k, {k, 1, nmax}] / ((1+x)*(1+x^2)*(1+x^3)*(1+x^4)), {x, 0, nmax}], x] (* Vaclav Kotesovec, Oct 30 2015 *)
CROSSREFS
Cf. A025147.
Sequence in context: A006141 A185229 A026825 * A026800 A185327 A210717
KEYWORD
nonn
STATUS
approved