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A076676
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Smallest a(n)>a(n-1) such that a(n)^2+a(n-1)^2 is a perfect square, a(1)=11.
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1
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11, 60, 63, 84, 112, 180, 189, 252, 275, 660, 693, 924, 1232, 1326, 1768, 1974, 2632, 4026, 5368, 6405, 8200, 8319, 11092, 11715, 15620, 16401, 19720, 20706, 20880, 20910, 24752, 24960, 25300, 26565, 29716, 29835, 33048, 35055, 41496, 42997
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OFFSET
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1,1
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COMMENTS
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The sequence is infinite.
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LINKS
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MAPLE
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q:= max(select(t -> n^2/t - t > 2*n and (t - n^2/t)::even, numtheory:-divisors(n^2)));
if q = -infinity then 0 else (n^2/q - q)/2 fi;
end proc:
A[1]:= 11;
for n from 2 to 100 do
od:
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MATHEMATICA
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nmax = 100;
q = Max[Select[Divisors[n^2], n^2/# - # > 2n &&
EvenQ[# - n^2/#]&]];
If[q == -Infinity, 0, (n^2/q - q)/2]];
a[1] = 11;
For[n = 2, n <= nmax, n++, a[n] = A076600[a[n - 1]]];
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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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