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A224214
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Number of nonnegative solutions to x^3 + y^3 <= n^3.
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3
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1, 3, 6, 11, 18, 26, 37, 50, 63, 80, 96, 115, 136, 159, 186, 210, 239, 268, 301, 336, 368, 407, 444, 487, 526, 574, 619, 664, 717, 764, 820, 875, 930, 989, 1047, 1112, 1175, 1238, 1307, 1375, 1444, 1521, 1592, 1669, 1745, 1828, 1907, 1988, 2073, 2161, 2252
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OFFSET
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0,2
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LINKS
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FORMULA
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a(n) = [x^(n^3)] (1/(1 - x))*(Sum_{k>=0} x^(k^3))^2. - Ilya Gutkovskiy, Apr 20 2018
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PROG
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(Python)
for a in range(99):
n = a*a*a
k = 0
for x in range(99):
s = x*x*x
if s>n: break
for y in range(99):
sy = s + y*y*y
if sy>n: break
k+=1
print(str(k), end=', ')
(PARI) a(n) = n++; p = Pol((1/(1 - x))*sum(k=0, n, x^(k^3))^2 + O(x^(n^3))); polcoeff(p, (n-1)^3); \\ Michel Marcus, Apr 21 2018
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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