A333995 - OEIS

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A333995

a(n) = number of distinct composite numbers in the n X n multiplication that are not in the n-1 X n-1 multiplication table.

0, 1, 2, 3, 4, 4, 6, 5, 6, 6, 10, 6, 12, 8, 9, 8, 16, 9, 18, 10, 12, 12, 22, 10, 16, 14, 15, 13, 28, 12, 30, 15, 18, 18, 20, 13, 36, 20, 21, 16, 40, 17, 42, 20, 21, 24, 46, 17, 31, 22, 27, 23, 52 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1,3`
	LINKS	`Table of n, a(n) for n=1..53.`
	FORMULA	`a(n) = n - A108407(n-1) - A010051(n), n>1. - Corrected by R. J. Mathar, Oct 02 2020`
	EXAMPLE	`a(2) = 1 since the 1X1 and 2X2 multiplication tables are` `---` `1` `---` `1 2` `2 4` `---` `and the composite number 4 has appeared.` `---` `a(8)=5:` `.1..2..3..4..5..6..7....8` `....4..6..8.10.12.14...16` `.......9.12.15.18.21...24` `.........16.20.24.28...32 ` `............25.30.35...40 ` `...............36.42...48 ` `..................49...56 ` `.......................64 *`
	CROSSREFS	`Cf. A010051, A108407.` `Sequence in context: A008328 A298933 A091860 * A301764 A181833 A202650` `Adjacent sequences: A333992 A333993 A333994 * A333996 A333997 A333998`
	KEYWORD	`nonn`
	AUTHOR	`Charles Kusniec, Sep 05 2020`
	STATUS	`approved`

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Last modified January 15 13:34 EST 2021. Contains 340187 sequences. (Running on oeis4.)