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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.)