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A215539
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First square that can be represented as the sum of n nonzero squares.
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2
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1, 25, 9, 4, 16, 9, 16, 16, 9, 16, 25, 36, 16, 25, 36, 16, 25, 36, 25, 36, 36, 25, 49, 36, 25, 49, 36, 36, 49, 36, 49, 49, 36, 49, 49, 36, 49, 49, 64, 49, 49, 64, 49, 64, 64, 49, 64, 64, 49, 64, 81, 64, 64, 81, 64, 64, 81, 64, 81, 81, 64, 81, 81, 64, 81, 81
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listen;
history;
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internal format)
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OFFSET
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1,2
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LINKS
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EXAMPLE
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a(1) = 1 = 1^2.
a(2) = 25 = 3^2 + 4^2.
a(3) = 9 = 1^2 + 2*2^2.
a(4) = 4 = 4*1^2.
a(5) = 16 = 3*1^2 + 2^2 + 3^2.
a(6) = 9 = 5*1^2 + 2^2.
a(7) = 16 = 4*1^2 + 3*2^2.
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MAPLE
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b:= proc(n, i, t) option remember; n>=t and (n=t or
(i>0 and (b(n, i-1, t) or i^2<=n and b(n-i^2, i, t-1))))
end:
a:= proc(n) option remember; local k;
for k while not b(k^2, k, n) do od; k^2
end:
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MATHEMATICA
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b[n_, i_, t_] := b[n, i, t] = n >= t && (n == t || (i > 0 && (b[n, i - 1, t] || i^2 <= n && b[n - i^2, i, t - 1])));
a[n_] := a[n] = Module[{k}, For[k = 1, !b[k^2, k, n], k++]; k^2];
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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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