A345569 Numbers that are the sum of seven fourth powers in three or more ways.

2677, 2692, 2757, 2852, 2867, 2917, 2932, 2997, 3107, 3172, 3301, 3476, 3541, 3972, 4132, 4147, 4212, 4227, 4242, 4257, 4307, 4322, 4372, 4387, 4437, 4452, 4482, 4497, 4562, 4627, 4737, 4756, 4851, 4866, 4867, 4931, 4996, 5077, 5106, 5107, 5122, 5187, 5252

Offset

1,1

Links

Sean A. Irvine, Table of n, a(n) for n = 1..10000

Example

2692 is a term because 2692 = 1^4 + 1^4 + 1^4 + 2^4 + 2^4 + 4^4 + 7^4 = 1^4 + 1^4 + 1^4 + 2^4 + 3^4 + 6^4 + 6^4 = 2^4 + 2^4 + 2^4 + 3^4 + 3^4 + 3^4 + 7^4.

Prog

(Python)
from itertools import combinations_with_replacement as cwr
from collections import defaultdict
keep = defaultdict(lambda: 0)
power_terms = [x**4 for x in range(1, 1000)]
for pos in cwr(power_terms, 7):
    tot = sum(pos)
    keep[tot] += 1
    rets = sorted([k for k, v in keep.items() if v >= 3])
    for x in range(len(rets)):
        print(rets[x])

Crossrefs

Cf. A345521, A345560, A345568, A345570, A345578, A345606, A345825.

Sequence in context: A345560 A345815 A166513 * A345825 A258505 A258512

Adjacent sequences: A345566 A345567 A345568 * A345570 A345571 A345572

Keyword

nonn

Author

David Consiglio, Jr., Jun 20 2021

Status

approved