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A025458 Number of partitions of n into 5 positive cubes. 3

%I #25 May 16 2021 01:55:58

%S 0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,1,0,1,

%T 0,0,0,0,1,0,1,0,0,0,0,1,0,0,0,0,0,0,1,0,0,0,0,1,0,1,0,0,0,0,1,0,0,0,

%U 1,0,0,1,0,0,0,1,0,0,1,0,0,0,1,1,0,0,0,0,0,1,1,0,0,0,1,0,1,1,0,0,0,1,0,0,0,0,0,0

%N Number of partitions of n into 5 positive cubes.

%C a(n) > 2 at n= 766, 810, 827, 829, 865, 883, 981, 1018, 1025, 1044,... - _R. J. Mathar_, Sep 15 2015

%C The first term > 1 is a(157) = 2. - _Michel Marcus_, Apr 25 2019

%H Robert Israel, <a href="/A025458/b025458.txt">Table of n, a(n) for n = 0..10000</a>

%H <a href="/index/Su#ssq">Index entries for sequences related to sums of cubes</a>

%F a(n) = [x^n y^5] Product_{k>=1} 1/(1 - y*x^(k^3)). - _Ilya Gutkovskiy_, Apr 23 2019

%p A025458 := proc(n)

%p local a,x,y,z,u,vcu ;

%p a := 0 ;

%p for x from 1 do

%p if 5*x^3 > n then

%p return a;

%p end if;

%p for y from x do

%p if x^3+4*y^3 > n then

%p break;

%p end if;

%p for z from y do

%p if x^3+y^3+3*z^3 > n then

%p break;

%p end if;

%p for u from z do

%p if x^3+y^3+z^3+2*u^3 > n then

%p break;

%p end if;

%p vcu := n-x^3-y^3-z^3-u^3 ;

%p if isA000578(vcu) then

%p a := a+1 ;

%p end if;

%p end do:

%p end do:

%p end do:

%p end do:

%p end proc: # _R. J. Mathar_, Sep 15 2015

%t a[n_] := IntegerPartitions[n, {5}, Range[n^(1/3) // Ceiling]^3] // Length;

%t a /@ Range[0, 157] (* _Jean-François Alcover_, Jun 20 2020 *)

%Y Column 5 of A320841, which cross-references the equivalent sequences for other numbers of positive cubes.

%Y Positions of values: A057906 (0), A003328 (nonzero), A048926 (1), A048927 (2), A343705 (3), A344035 (4).

%K nonn

%O 0,158

%A _David W. Wilson_

%E Second offset from _Michel Marcus_, Apr 25 2019

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Last modified May 15 07:58 EDT 2024. Contains 372538 sequences. (Running on oeis4.)