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A181138
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Least positive integer k such that n^2 + k is a cube.
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8
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1, 7, 4, 18, 11, 2, 28, 15, 61, 44, 25, 4, 72, 47, 20, 118, 87, 54, 19, 151, 112, 71, 28, 200, 153, 104, 53, 271, 216, 159, 100, 39, 307, 242, 175, 106, 35, 359, 284, 207, 128, 47, 433, 348, 261, 172, 81, 535, 440, 343, 244, 143, 40, 566, 459, 350, 239, 126, 11
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OFFSET
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0,2
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COMMENTS
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See A229618 for the range of this sequence. A179386 gives the range of b(n) = min{ a(m); m >= n }. The indices of jumps in this sequence are given in A179388 = { n | a(m)>a(n) for all m > n } = { 0, 5, 11, 181, 207, 225, 500, 524, 1586, ... }. - M. F. Hasler, Sep 26 2013
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LINKS
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FORMULA
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EXAMPLE
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a(11) = 4 because 11^2 + k is never a cube for k < 4, but 11^2 + 4 = 5^3. - Bruno Berselli, Jan 29 2013
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MATHEMATICA
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Table[(1 + Floor[n^(2/3)])^3 - n^2, {n, 100}] (* Zak Seidov, Mar 26 2013 *)
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PROG
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(Magma)
S:=[];
k:=1;
for n in [0..60] do
while not IsPower(n^2+k, 3) do
k:=k+1;
end while;
Append(~S, k);
k:=1;
end for;
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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