OFFSET
1,2
LINKS
Seiichi Manyama, Table of n, a(n) for n = 1..1000
EXAMPLE
If the {s+t} sums are generated by addition 2 terms of an S set consisting of n different entries, then at least 1, at most n(n+1)/2=A000217(n) distinct values can be obtained. The set of first n cubes gives results falling between these two extremes. E.g. S={1,8,27,...,2744,3375} provides 119 different sums of two, not necessarily different cubes:{2,9,....,6750}. Only a single sum occurs more than once: 1729(Ramanujan): 1729=1+1728=729+1000.
MATHEMATICA
f[x_] := x^3 t=Table[Length[Union[Flatten[Table[f[u]+f[w], {w, 1, m}, {u, 1, m}]]]], {m, 1, 75}]
PROG
(Ruby)
def A(n)
h = {}
(1..n).each{|i|
(i..n).each{|j|
k = i * i * i + j * j * j
if h.has_key?(k)
h[k] += 1
else
h[k] = 1
end
}
}
h.size
end
def A061791(n)
(1..n).map{|i| A(i)}
end
p A061791(60) # Seiichi Manyama, May 14 2024
CROSSREFS
KEYWORD
nonn
AUTHOR
Labos Elemer, Jun 22 2001
STATUS
approved