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A057144 Smallest of the most frequently occurring numbers in 1-to-n multiplication table. 10
1, 2, 2, 4, 4, 6, 6, 6, 6, 6, 6, 12, 12, 12, 12, 12, 12, 36, 36, 60, 60, 60, 60, 24, 24, 24, 24, 24, 24, 60, 60, 60, 60, 60, 60, 60, 60, 60, 60, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120, 120 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,2

LINKS

Reinhard Zumkeller, Table of n, a(n) for n = 1..1000

Benjamin Dickman, What number appears most often in an n X n multiplication table?, Mathematics StackExchange, May 2014.

EXAMPLE

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 smallest of these numbers is 6, so a(10) = 6.

PROG

(Haskell)

import Data.List (sort, group, sortBy, groupBy)

import Data.Function (on)

a057144 n = head $ last $ head $ groupBy ((==) `on` length) $

            reverse $ sortBy (compare `on` length) $

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

-- Reinhard Zumkeller, Jun 22 2013

CROSSREFS

Cf. A057142, A057143, A057338.

Sequence in context: A007730 A330271 A257686 * A198332 A080606 A083535

Adjacent sequences:  A057141 A057142 A057143 * A057145 A057146 A057147

KEYWORD

nonn

AUTHOR

Arran Fernandez, Aug 13 2000

EXTENSIONS

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

STATUS

approved

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Last modified May 15 18:13 EDT 2021. Contains 343920 sequences. (Running on oeis4.)