OFFSET
0,252
COMMENTS
If A025455(n) > 0 then a(n + k^3) > 0 for k>0; a(A119977(n))>0; a(A003072(n))>0. - Reinhard Zumkeller, Jun 03 2006
a(A057904(n))=0; a(A003072(n))>0; a(A025395(n))=1; a(A008917(n))>1; a(A025396(n))=2. - Reinhard Zumkeller, Apr 23 2009
The first term > 1 is a(251) = 2. - Michel Marcus, Apr 23 2019
LINKS
Charles R Greathouse IV, Table of n, a(n) for n = 0..10000
FORMULA
a(n) = [x^n y^3] Product_{k>=1} 1/(1 - y*x^(k^3)). - Ilya Gutkovskiy, Apr 23 2019
MAPLE
A025456 := proc(n)
local a, x, y, zcu ;
a := 0 ;
for x from 1 do
if 3*x^3 > n then
return a;
end if;
for y from x do
if x^3+2*y^3 > n then
break;
end if;
zcu := n-x^3-y^3 ;
if isA000578(zcu) then
a := a+1 ;
end if;
end do:
end do:
end proc: # R. J. Mathar, Sep 15 2015
MATHEMATICA
a[n_] := Count[ PowersRepresentations[n, 3, 3], pr_List /; FreeQ[pr, 0]]; Table[a[n], {n, 0, 107}] (* Jean-François Alcover, Oct 31 2012 *)
PROG
(PARI) a(n)=sum(a=sqrtnint(n\3, 3), sqrtnint(n, 3), sum(b=1, a, my(C=n-a^3-b^3, c); ispower(C, 3, &c)&&0<c&&c<=b)) \\ Charles R Greathouse IV, Jun 26 2013
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Second offset from Michel Marcus, Apr 23 2019
STATUS
approved