id:A163108 - OEIS Search Results

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sigma (tau (sigma (n)))

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1, 3, 4, 3, 7, 12, 7, 7, 3, 12, 12, 12, 7, 15, 15, 3, 12, 7, 12, 15, 12, 13, 15, 28, 3, 15, 15, 15, 15, 28, 12, 12, 18, 15, 18, 7, 7, 28, 15, 28, 15, 28, 12, 28, 15, 28, 18, 12, 7, 7, 28, 12, 15, 31, 28, 31, 18, 28, 28, 31, 7, 28, 15, 3, 28, 24, 12, 28, 28, 24, 28, 15, 7, 15, 12, 28, 28 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`Repeated application of tau (number of divisors) and sigma (sum of divisors).`
	FORMULA	`a(n) = A000203(A000005(A000203(n))) = A000203(A062068(n)) = A062069(A000203(n)).`
	MAPLE	`with(numtheory) : A163108 := proc(n) sigma(tau(sigma(n))) ; end: seq(A163108(n), n=1..120) ; # R. J. Mathar, Jul 27 2009`
	CROSSREFS	`Sequence in context: A111970 A141730 A127737 this_sequence A077005 A134065 A015887` `Adjacent sequences: A163105 A163106 A163107 this_sequence A163109 A163110 A163111`
	KEYWORD	`nonn`
	AUTHOR	`Jaroslav Krizek (jaroslav.krizek(AT)atlas.cz), Jul 20 2009`
	EXTENSIONS	`More terms from R. J. Mathar (mathar(AT)strw.leidenuniv.nl), Jul 27 2009`

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Last modified December 16 13:01 EST 2009. Contains 170825 sequences.

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