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A057143 Largest of the most frequently occurring numbers in 1-to-n multiplication table. 7

%I #19 Mar 29 2022 08:36:41

%S 1,2,6,4,4,12,12,24,24,40,40,24,24,24,60,60,60,36,36,60,60,60,60,120,

%T 120,120,120,168,168,120,120,120,120,120,120,180,180,180,180,120,120,

%U 120,120,120,360,360,360,360,360,360,360,360,360,360,360,360,360,360

%N Largest of the most frequently occurring numbers in 1-to-n multiplication table.

%H Branden Aldridge, <a href="/A057143/b057143.txt">Table of n, a(n) for n = 1..20000</a> (first 1000 terms from Reinhard Zumkeller).

%e M(n) is the array in which m(x,y)= x*y for x = 1 to n and y = 1 to n. In M(10), the most frequently occurring numbers are 6, 8, 10, 12, 18, 20, 24, 30,40, each occurring 4 times. The largest of these numbers is 40, so a(10) = 40.

%o (Haskell)

%o import Data.List (group, sort, sortBy)

%o import Data.Function (on)

%o a057143 n = head $ head $ reverse $ sortBy (compare `on` length) $

%o group $ sort [u * v | u <- [1..n], v <- [1..n]]

%o -- _Reinhard Zumkeller_, Jun 22 2013

%Y Cf. A057142, A057144, A057338.

%K nonn

%O 1,2

%A _Arran Fernandez_, Aug 13 2000

%E More terms from Larry Reeves (larryr(AT)acm.org), Apr 18 2001

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Last modified July 22 23:01 EDT 2024. Contains 374544 sequences. (Running on oeis4.)