id:A081386 - OEIS Search Results

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Number of unitary prime divisors of central binomial coefficient, C[2n,n]=A000984(n), i.e. number of those prime-factors in C[2n,n], whose exponent equals one.

+0
8

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

	OFFSET	`1,2`
	LINKS	`T. D. Noe, Table of n, a(n) for n=1..2000`
	FORMULA	`a(n) = A056169[A000984(n)]`
	EXAMPLE	`n=10: C[20,10]=184756=2.2.11.13.17.19; unitary-p-divisors={11,13,17,19}, so a(10)=4`
	CROSSREFS	`Cf. A000984, A067434, A081387-A081389, A034444, A048105, A056170, A056169.` `Adjacent sequences: A081383 A081384 A081385 this_sequence A081387 A081388 A081389` `Sequence in context: A111248 A100714 A050123 this_sequence A143802 A135591 A114897`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), Mar 27 2003`

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Last modified October 11 13:47 EDT 2008. Contains 144830 sequences.

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