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Max ( sigma(x*y) : 1<=x<=n, 1<=y<=n ).
3

%I #24 Feb 12 2018 10:24:55

%S 1,7,13,31,42,91,96,127,195,234,234,403,403,480,576,744,744,847,847,

%T 1170,1344,1344,1344,1651,1860,1860,1860,2240,2240,2880,2880,3048,

%U 3048,3048,3048,4368,4368,4368,4368,5040,5040,5952,5952,5952,6552,6552,6552

%N Max ( sigma(x*y) : 1<=x<=n, 1<=y<=n ).

%C 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.

%H Reinhard Zumkeller, <a href="/A074963/b074963.txt">Table of n, a(n) for n = 1..750</a>

%p A074963 := proc(n)

%p a := 0 ;

%p for x from 1 to n do

%p for y from 1 to x do

%p a := max(a, numtheory[sigma](x*y)) ;

%p end do:

%p end do;

%p a ;

%p end proc: # _R. J. Mathar_, Sep 27 2011

%t 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 *)

%o (PARI) a(n)=vecmax(matrix(n,n,x,y, sigma(x*y)))

%o (Haskell)

%o a074963 n = maximum [a000203 (x*y) | x <- [1..n], y <- [x..n]]

%o -- _Reinhard Zumkeller_, Nov 14 2011

%Y Cf. A000203.

%K easy,nonn

%O 1,2

%A _Benoit Cloitre_, Oct 05 2002