id:A047983 - OEIS Search Results

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Number of integers less than n but with the same number of divisors.

+0
2

0, 0, 1, 0, 2, 0, 3, 1, 1, 2, 4, 0, 5, 3, 4, 0, 6, 1, 7, 2, 5, 6, 8, 0, 2, 7, 8, 3, 9, 1, 10, 4, 9, 10, 11, 0, 11, 12, 13, 2, 12, 3, 13, 5, 6, 14, 14, 0, 3, 7, 15, 8, 15, 4, 16, 5, 17, 18, 16, 0, 17, 19, 9, 0, 20, 6, 18, 10, 21, 7, 19, 1, 20, 22, 11, 12, 23, 8, 21, 1, 1, 24, 22, 2, 25, 26, 27 (list; graph; listen)

	OFFSET	`1,5`
	COMMENT	`Invented by the HR concept formation program.`
	LINKS	`T. D. Noe, Table of n, a(n) for n=1..10000` `S. Colton, Refactorable Numbers - A Machine Invention, J. Integer Sequences, Vol. 2, 1999, #2.` `S. Colton, HR - Automatic Theory Formation in Pure Mathematics`
	FORMULA	`f(n) = \|{a < n : tau(a)=tau(n)}\|`
	EXAMPLE	`f(10) = 2 because tau(10)=4 and also tau(6)=tau(8)=4.`
	CROSSREFS	`Position of the 0's form A007416. Cf. A005179.` `Sequence in context: A124756 A113504 A124754 this_sequence A070812 A061865 A135818` `Adjacent sequences: A047980 A047981 A047982 this_sequence A047984 A047985 A047986`
	KEYWORD	`nice,nonn`
	AUTHOR	`Simon Colton (simonco(AT)cs.york.ac.uk)`

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Last modified November 25 20:09 EST 2009. Contains 167514 sequences.

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