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A251781 Numbers whose square is the sum of two distinct positive cubes. 1
3, 24, 81, 98, 168, 192, 228, 312, 375, 525, 588, 648, 671, 784, 847, 1014, 1029, 1183, 1225, 1261, 1323, 1344, 1536, 1824, 2187, 2496, 2646, 2888, 3000, 3993, 4200, 4225, 4536, 4563, 4644, 4704, 5184, 5368, 6156, 6272, 6292, 6371, 6591, 6696, 6776, 6877, 8112 (list; graph; refs; listen; history; text; internal format)
OFFSET
1,1
COMMENTS
This list contains A117642 (if n=3*k^3, then n^2 = 9*k^6 = 8*k^6 + k^6 = (2*k^2)^3 + (k^2)^3). (Old comment rewritten as suggested by Michel Marcus, Dec 10 2014.)
Subsequence of A050801 and A217248. - Wolfdieter Lang, Jan 04 2015
LINKS
EXAMPLE
3^2 = 1^3 + 2^3; 24^2 = 4^3 + 8^3.
PROG
(Sage)
L = []
for k in range(1, 10^3):
for l in range(k + 1, 10^3):
if is_square(k**3+l**3):
L.append(sqrt(k**3+l**3))
(Python)
def aupto(limit):
c = [i**3 for i in range(1, int(limit**(2/3))+2) if i**3 <= limit**2]
cc = [c1 + c2 for i, c1 in enumerate(c) for c2 in c[i+1:]]
return sorted([i for i in range(1, limit+1) if i*i in cc])
print(aupto(8122)) # Michael S. Branicky, Mar 24 2021
CROSSREFS
Cf. A024670, A117642, A050801, A217248, A099426 (coprime positive cubes).
Sequence in context: A092468 A347108 A027158 * A117642 A220834 A276243
KEYWORD
nonn
AUTHOR
Daniel Arribas, Dec 08 2014
STATUS
approved

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Last modified May 18 18:37 EDT 2024. Contains 372664 sequences. (Running on oeis4.)