A343969 Numbers that are the sum of three positive cubes in exactly 4 ways.

13896, 40041, 44946, 52200, 53136, 58995, 76168, 82278, 93339, 94184, 105552, 110683, 111168, 112384, 112832, 113400, 143424, 149416, 149904, 167616, 169560, 171296, 175104, 196776, 197569, 208144, 216126, 221696, 222984, 224505, 235808, 240813, 252062, 255312, 262781, 266031, 281728, 291213

Offset

1,1

Comments

Differs from A343968 at term 20 because 161568 = 2^3 + 16^3 + 54^3 = 9^3 + 15^3 + 54^3 = 17^3 + 39^3 + 46^3 = 18^3 + 19^3 + 53^3 = 26^3 + 36^3 + 46^3.

Links

David Consiglio, Jr., Table of n, a(n) for n = 1..20000

Example

44946 is a term because 44946 = 7^3 + 12^3 + 35^3 = 9^3 + 17^3 + 34^3 = 11^3 + 24^3 + 31^3 = 16^3 + 17^3 + 33^3.

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, 50)]
for pos in cwr(power_terms, 3):
    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. A025324, A025397, A343968, A343970, A343972, A344278, A345865.

Sequence in context: A237941 A343085 A343968 * A190817 A298428 A252557

Adjacent sequences: A343966 A343967 A343968 * A343970 A343971 A343972

Keyword

nonn

Author

David Consiglio, Jr., May 05 2021

Status

approved