OFFSET
0,10
COMMENTS
Number of ways to write n as an ordered sum of two positive cubes.
LINKS
Antti Karttunen, Table of n, a(n) for n = 0..65537
Eric Weisstein's World of Mathematics, Cubic Number
FORMULA
G.f.: (Sum_{k>=1} x^(k^3))^2.
EXAMPLE
a(9) = 2 because we have [8, 1] and [1, 8].
MATHEMATICA
nmax = 150; CoefficientList[Series[(Sum[x^(k^3), {k, 1, nmax}])^2, {x, 0, nmax}], x]
PROG
(PARI)
A010057(n) = ispower(n, 3);
A280618(n) = if(n<2, 0, sum(r=1, sqrtnint(n-1, 3), A010057(n-(r^3)))); \\ Antti Karttunen, Nov 30 2021
CROSSREFS
KEYWORD
nonn
AUTHOR
Ilya Gutkovskiy, Jan 06 2017
STATUS
approved