A343987 Numbers that are the sum of four positive cubes in five or more ways.

5105, 5131, 5616, 5859, 6435, 6883, 7777, 9315, 9737, 9793, 10017, 10250, 10458, 10936, 10962, 11000, 11060, 11088, 11592, 11664, 11781, 12168, 12229, 12285, 12320, 12385, 12392, 12411, 12707, 13104, 13384, 13734, 13832, 13904, 13923, 14112, 14183, 14239, 14581, 14833, 14896, 14904, 15176, 15561, 15596

Offset

1,1

Links

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

Example

5616 is a term because 5616 = 1^3 + 8^3 + 12^3 + 15^3 = 2^3 + 8^3 + 10^3 + 16^3 = 4^3 + 4^3 + 14^3 + 14^3 = 4^3 + 5^3 + 11^3 + 16^3 = 8^3 + 9^3 + 10^3 + 15^3.

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, 4):
    tot = sum(pos)
    keep[tot] += 1
rets = sorted([k for k, v in keep.items() if v >= 5])
for x in range(len(rets)):
    print(rets[x], end=", ")

Crossrefs

Cf. A025370, A343967, A343971, A343986, A343989, A344356, A345148.

Sequence in context: A025397 A025402 A025401 * A343986 A255209 A261462

Adjacent sequences: A343984 A343985 A343986 * A343988 A343989 A343990

Keyword

nonn

Author

David Consiglio, Jr., May 06 2021

Status

approved