A345479 Numbers that are the sum of seven squares in two or more ways.

22, 25, 28, 30, 31, 33, 34, 37, 38, 39, 40, 42, 43, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96

Offset

1,1

Links

Sean A. Irvine, Table of n, a(n) for n = 1..1000

Example

25 = 1^2 + 1^2 + 1^2 + 1^2 + 1^2 + 2^2 + 4^2
   = 1^2 + 2^2 + 2^2 + 2^2 + 2^2 + 2^2 + 2^2
so 25 is a term.

Prog

(Python)
from itertools import combinations_with_replacement as cwr
from collections import defaultdict
keep = defaultdict(lambda: 0)
power_terms = [x**2 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 >= 2])
    for x in range(len(rets)):
        print(rets[x])

Crossrefs

Cf. A344806, A345478, A345480, A345489, A345520.

Sequence in context: A254753 A070809 A280646 * A295799 A338603 A322124

Adjacent sequences: A345476 A345477 A345478 * A345480 A345481 A345482

Keyword

nonn

Author

David Consiglio, Jr., Jun 20 2021

Status

approved