A345786 Numbers that are the sum of eight cubes in exactly four ways.

256, 347, 382, 401, 408, 427, 434, 438, 445, 464, 478, 480, 490, 499, 502, 506, 511, 516, 523, 530, 532, 534, 537, 560, 565, 567, 569, 571, 578, 586, 593, 595, 600, 602, 604, 605, 611, 612, 616, 619, 621, 624, 626, 643, 645, 656, 660, 663, 664, 668, 675, 679

Offset

1,1

Comments

Differs from A345534 at term 11 because 471 = 1^3 + 1^3 + 1^3 + 1^3 + 1^3 + 5^3 + 5^3 + 6^3 = 1^3 + 1^3 + 1^3 + 1^3 + 2^3 + 3^3 + 6^3 + 6^3 = 1^3 + 1^3 + 3^3 + 4^3 + 4^3 + 4^3 + 5^3 + 5^3 = 1^3 + 2^3 + 3^3 + 3^3 + 4^3 + 4^3 + 4^3 + 6^3 = 2^3 + 2^3 + 2^3 + 2^3 + 4^3 + 5^3 + 5^3 + 5^3.

Likely finite.

Links

Sean A. Irvine, Table of n, a(n) for n = 1..207

Example

347 is a term because 347 = 1^3 + 1^3 + 1^3 + 1^3 + 1^3 + 1^3 + 4^3 + 5^3 = 1^3 + 1^3 + 1^3 + 3^3 + 3^3 + 3^3 + 3^3 + 4^3 = 1^3 + 2^3 + 2^3 + 2^3 + 2^3 + 3^3 + 4^3 + 4^3 = 2^3 + 2^3 + 2^3 + 2^3 + 2^3 + 3^3 + 3^3 + 5^3.

Prog

(Python)
from itertools import combinations_with_replacement as cwr
from collections import defaultdict
keep = defaultdict(lambda: 0)
power_terms = [x**3 for x in range(1, 1000)]
for pos in cwr(power_terms, 8):
    tot = sum(pos)
    keep[tot] += 1
    rets = sorted([k for k, v in keep.items() if v == 4])
    for x in range(len(rets)):
        print(rets[x])

Crossrefs

Cf. A345534, A345776, A345785, A345787, A345796, A345836.

Sequence in context: A044979 A352595 A345534 * A186473 A046309 A036332

Adjacent sequences: A345783 A345784 A345785 * A345787 A345788 A345789

Keyword

nonn

Author

David Consiglio, Jr., Jun 26 2021

Status

approved