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A074963
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Max ( sigma(x*y) : 1<=x<=n, 1<=y<=n ).
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3
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1, 7, 13, 31, 42, 91, 96, 127, 195, 234, 234, 403, 403, 480, 576, 744, 744, 847, 847, 1170, 1344, 1344, 1344, 1651, 1860, 1860, 1860, 2240, 2240, 2880, 2880, 3048, 3048, 3048, 3048, 4368, 4368, 4368, 4368, 5040, 5040, 5952, 5952, 5952, 6552, 6552, 6552
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OFFSET
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1,2
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COMMENTS
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Does a(n)=sigma(n^2) for a finite number of values of n (1,2,3,4,6,8,12,18,24,60)? See A074964.
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LINKS
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MAPLE
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a := 0 ;
for x from 1 to n do
for y from 1 to x do
a := max(a, numtheory[sigma](x*y)) ;
end do:
end do;
a ;
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MATHEMATICA
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a[n_] := Module[{m = 0}, Do[m = Max[m, DivisorSigma[1, x*y]], {x, 1, n}, {y, 1, x}]; m]; Array[a, 50] (* Jean-François Alcover, Feb 12 2018 *)
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PROG
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(PARI) a(n)=vecmax(matrix(n, n, x, y, sigma(x*y)))
(Haskell)
a074963 n = maximum [a000203 (x*y) | x <- [1..n], y <- [x..n]]
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CROSSREFS
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KEYWORD
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easy,nonn
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AUTHOR
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STATUS
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approved
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