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A025362
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Numbers that are the sum of 4 nonzero squares in exactly 6 ways.
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4
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90, 124, 133, 147, 156, 157, 159, 163, 165, 166, 171, 174, 177, 188, 193, 201, 203, 205, 219, 239, 241, 249, 254, 260, 284, 293, 299, 329, 341, 360, 496, 624, 664, 696, 752, 1016, 1040, 1136, 1440, 1984, 2496, 2656, 2784, 3008, 4064, 4160, 4544, 5760, 7936
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OFFSET
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1,1
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LINKS
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PROG
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(Python)
limit = 8000
from functools import lru_cache
sq = [k**2 for k in range(1, int(limit**.5)+2) if k**2 + 3 <= limit]
sqs = set(sq)
@lru_cache(maxsize=None)
def findsums(n, m):
if m == 1: return {(n, )} if n in sqs else set()
return set(tuple(sorted(t+(s, ))) for s in sqs for t in findsums(n-s, m-1))
print([n for n in range(4, limit+1) if len(findsums(n, 4)) == 6]) # Michael S. Branicky, Apr 20 2021
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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STATUS
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approved
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