A339990 Sums of two odd cubes.

2, 28, 54, 126, 152, 250, 344, 370, 468, 686, 730, 756, 854, 1072, 1332, 1358, 1456, 1458, 1674, 2060, 2198, 2224, 2322, 2540, 2662, 2926, 3376, 3402, 3500, 3528, 3718, 4104, 4394, 4706, 4914, 4940, 5038, 5256, 5572, 5642, 6244, 6750, 6860, 6886, 6984, 7110, 7202

Offset

1,1

Links

Table of n, a(n) for n=1..47.

Example

28 is in the sequence since 1^3 + 3^3 = 1 + 27 = 28, with 1 and 27 both odd.

Mathematica

Table[If[Sum[Mod[i, 2] Mod[n - i, 2] (Floor[i^(1/3)] - Floor[(i - 1)^(1/3)]) (Floor[(n - i)^(1/3)] - Floor[(n - i - 1)^(1/3)]), {i, Floor[n/2]}] > 0, n, {}], {n, 1200}] // Flatten
Union[Total/@Tuples[Range[1, 25, 2]^3, 2]] (* Harvey P. Dale, Nov 17 2024 *)

Prog

(Python)
def aupto(lim):
  ocs = [k**3 for k in range(1, int(lim**(1/3)+2), 2)]
  return sorted(set(c1+c2 for c1 in ocs for c2 in ocs if c1+c2 <= lim))
print(aupto(7202)) # Michael S. Branicky, Feb 28 2021

Crossrefs

Cf. A010057.

Sequence in context: A022376 A177829 A363875 * A336464 A245801 A296245

Adjacent sequences: A339987 A339988 A339989 * A339991 A339992 A339993

Keyword

nonn

Author

Wesley Ivan Hurt, Dec 25 2020

Status

approved