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a(n)=d[ d[ d[ d[ n ] ] ] ], the 4th iterate of number-of-divisors function with initial value of n.

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1, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 3, 2, 2, 2, 2, 2, 2, 2, 2, 2 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`The iterated d function rapidly converges to fixed point 2. For k=4 the first n for which a(n)>2 is 60.`
	FORMULA	`a[ n ]=Nest[ d, n, 4 ]`
	EXAMPLE	`E.g. n=96 and its successive iterates are 12,6,4,3 and 2. The 4th term is a(96)=3.`
	CROSSREFS	`A000005, A015553, A036450, A036453.` `Sequence in context: A007395 A055642 A138902 this_sequence A102572 A098391 A071702` `Adjacent sequences: A036449 A036450 A036451 this_sequence A036453 A036454 A036455`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu)`

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

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