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A066213
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Numbers which are sums of squares of some subset of divisors.
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4
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1, 4, 9, 16, 20, 25, 30, 36, 49, 64, 80, 81, 90, 100, 120, 121, 126, 130, 144, 150, 169, 180, 195, 196, 210, 225, 252, 256, 264, 270, 272, 280, 289, 294, 300, 315, 320, 324, 330, 336, 350, 360, 361, 378, 390, 396, 400, 414, 420, 441, 450, 468, 480, 484, 500
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listen;
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OFFSET
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1,2
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COMMENTS
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If m is in the sequence then so is m*k^2 for k >= 1. - David A. Corneth, Jan 22 2024
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LINKS
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EXAMPLE
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20 is in the list since 20 = 2^2 + 4^2 and 2 and 4 are divisors of 20
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MAPLE
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isA066213 := proc(n)
local S, els;
S:=subsets(numtheory[divisors](n));
while not S[finished] do
els:=S[nextvalue]() ;
if add(d^2, d=els) = n then
return true ;
end if ;
end do;
false
end proc:
for n from 1 do
if isA066213(n) then
print(n) ;
end if;
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PROG
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(PARI) \\ See PARI link
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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