id:A081387 - OEIS Search Results

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Number of non-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 is greater than one.

+0
6

0, 0, 1, 0, 2, 1, 1, 1, 1, 1, 1, 1, 2, 3, 2, 1, 2, 2, 2, 2, 1, 1, 3, 3, 3, 3, 2, 1, 1, 1, 1, 2, 2, 2, 2, 1, 1, 2, 3, 2, 3, 2, 3, 3, 2, 3, 3, 4, 3, 2, 2, 2, 2, 1, 1, 2, 1, 1, 2, 2, 3, 3, 3, 2, 4, 2, 2, 3, 3, 3, 3, 4, 4, 5, 4, 4, 2, 3, 3, 2, 2, 2, 4, 3, 3, 4, 3, 4, 5, 4, 2, 2, 2, 3, 5, 5, 5, 5, 3, 2, 3, 2, 3, 3, 3 (list; graph; listen)

	OFFSET	`1,5`
	LINKS	`T. D. Noe, Table of n, a(n) for n=1..10000`
	FORMULA	`a(n)=A056170[A000984(n)]=A001221[A000984(n)]-A081386(n)= A067434(n)-A081386(n).`
	EXAMPLE	`n=14: C[28,14]=40116600=2.2.2.3.3.3.5.5.17.19.23, unitary-p-divisors={17,19,23}, non-unitary p-divisors={2,3,5}, so a(14)=3.`
	CROSSREFS	`Cf. A000984, A067434, A081387-A081389, A034444, A048105, A056170, A056169.` `Adjacent sequences: A081384 A081385 A081386 this_sequence A081388 A081389 A081390` `Sequence in context: A116531 A101871 A101875 this_sequence A059895 A117358 A062378`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), Mar 27 2003`

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Last modified October 13 20:18 EDT 2008. Contains 145016 sequences.

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