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A224214 Number of nonnegative solutions to x^3 + y^3 <= n^3. 3
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 (list; graph; refs; listen; history; text; internal format)
OFFSET

0,2

LINKS

Table of n, a(n) for n=0..50.

FORMULA

a(n) = [x^(n^3)] (1/(1 - x))*(Sum_{k>=0} x^(k^3))^2. - Ilya Gutkovskiy, Apr 20 2018

PROG

(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

CROSSREFS

Sequence in context: A340648 A140126 A140235 * A010000 A183199 A172046

Adjacent sequences: A224211 A224212 A224213 * A224215 A224216 A224217

KEYWORD

nonn

AUTHOR

Alex Ratushnyak, Apr 01 2013

STATUS

approved

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Last modified January 30 19:31 EST 2023. Contains 359947 sequences. (Running on oeis4.)