A345825 Numbers that are the sum of seven fourth powers in exactly three ways.

2677, 2692, 2757, 2852, 2867, 2917, 2997, 3107, 3172, 3301, 3476, 3541, 3972, 4132, 4227, 4242, 4257, 4307, 4322, 4372, 4437, 4452, 4482, 4497, 4562, 4627, 4737, 4756, 4851, 4866, 4867, 4931, 4996, 5077, 5106, 5107, 5122, 5187, 5252, 5282, 5317, 5347, 5362

Offset

1,1

Comments

Differs from A345569 at term 7 because 2932 = 1^4 + 1^4 + 1^4 + 2^4 + 4^4 + 4^4 + 7^4 = 1^4 + 1^4 + 1^4 + 3^4 + 4^4 + 6^4 + 6^4 = 2^4 + 2^4 + 3^4 + 3^4 + 3^4 + 4^4 + 7^4 = 2^4 + 3^4 + 3^4 + 3^4 + 3^4 + 6^4 + 6^4.

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. A345569, A345775, A345815, A345824, A345826, A345835, A346280.

Sequence in context: A345815 A166513 A345569 * A258505 A258512 A254992

Adjacent sequences: A345822 A345823 A345824 * A345826 A345827 A345828

Keyword

nonn

Author

David Consiglio, Jr., Jun 26 2021

Status

approved