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 A074963 Max ( sigma(x*y) : 1<=x<=n, 1<=y<=n ). 3
 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 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,2 COMMENTS 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. LINKS Reinhard Zumkeller, Table of n, a(n) for n = 1..750 MAPLE A074963 := proc(n)         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 ; end proc: # R. J. Mathar, Sep 27 2011 MATHEMATICA 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 *) PROG (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]] -- Reinhard Zumkeller, Nov 14 2011 CROSSREFS Cf. A000203. Sequence in context: A046139 A023243 A087196 * A283937 A231626 A110912 Adjacent sequences:  A074960 A074961 A074962 * A074964 A074965 A074966 KEYWORD easy,nonn AUTHOR Benoit Cloitre, Oct 05 2002 STATUS approved

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Last modified October 21 06:39 EDT 2019. Contains 328292 sequences. (Running on oeis4.)