A057567 Number of partitions of n where the product of parts divides n.
1, 2, 2, 4, 2, 5, 2, 7, 4, 5, 2, 11, 2, 5, 5, 12, 2, 11, 2, 11, 5, 5, 2, 21, 4, 5, 7, 11, 2, 15, 2, 19, 5, 5, 5, 26, 2, 5, 5, 21, 2, 15, 2, 11, 11, 5, 2, 38, 4, 11, 5, 11, 2, 21, 5, 21, 5, 5, 2, 36, 2, 5, 11, 30, 5, 15, 2, 11, 5, 15, 2, 52, 2, 5, 11, 11, 5, 15, 2, 38, 12, 5, 2, 36, 5, 5, 5, 21
Offset: 1
Keywords
Examples
From _Gus Wiseman_, Jul 04 2019: (Start) The a(1) = 1 through a(9) = 5 partitions are the following. The Heinz numbers of these partitions are given by A326155. (1) (2) (3) (4) (5) (6) (7) (8) (11) (111) (22) (11111) (321) (1111111) (4211) (211) (3111) (22211) (1111) (21111) (41111) (111111) (221111) (2111111) (11111111) (End)
Links
Crossrefs
Programs
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Mathematica
Table[Function[m, Count[Map[Times @@ # &, IntegerPartitions[m]], P_ /; Divisible[m, P]] - Boole[n == 1]]@ Apply[Times, #] &@ MapIndexed[Prime[First@ #2]^#1 &, Sort[FactorInteger[n][[All, -1]], Greater]], {n, 88}] (* Michael De Vlieger, Aug 16 2017 *)
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PARI
fcnt(n, m) = {local(s); s=0; if(n == 1, s=1, fordiv(n, d, if(d > 1 & d <= m, s=s+fcnt(n/d, d)))); s} A001055(n) = fcnt(n, n) \\ This function from Michael B. Porter, Oct 29 2009 A057567(n) = sumdiv(n, d, A001055(d)); \\ After Jovovic's formula. Antti Karttunen, May 25 2017
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Python
from sympy import divisors, isprime def T(n, m): if isprime(n): return 1 if n <= m else 0 A = (d for d in divisors(n) if 1 < d < n and d <= m) s = sum(T(n // d, d) for d in A) return s + 1 if n <= m else s def a001055(n): return T(n, n) def a(n): return sum(a001055(d) for d in divisors(n)) print([a(n) for n in range(1, 51)]) # Indranil Ghosh, Aug 19 2017
Formula
a(n) = Sum_{d|n} A001055(d). - Vladeta Jovovic, Nov 19 2000
a(p^k) = A000070(k).
Dirichlet g.f.: zeta(s) * Product_{k>=2} 1/(1 - 1/k^s). - Ilya Gutkovskiy, Nov 03 2020
Extensions
More terms from James Sellers, Oct 09 2000
More terms from Vladeta Jovovic, Nov 19 2000
Comments