id:A056648 - OEIS Search Results

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Number of unitary square divisors of central binomial coefficient.

+0
1

1, 1, 1, 1, 1, 2, 1, 1, 2, 4, 1, 2, 2, 1, 2, 2, 1, 2, 1, 2, 2, 1, 1, 2, 4, 2, 4, 2, 2, 4, 2, 2, 1, 2, 2, 4, 4, 2, 2, 4, 2, 1, 2, 1, 2, 4, 4, 8, 8, 4, 4, 2, 2, 4, 2, 1, 1, 2, 1, 2, 2, 2, 4, 4, 2, 4, 2, 4, 4, 2, 1, 2, 2, 1, 4, 2, 4, 8, 2, 4, 8, 4, 2, 1, 2, 4, 8, 4, 2, 4, 4, 8, 4, 4, 8, 16, 8, 4, 4, 2, 1, 2, 2, 1 (list; graph; listen)

	OFFSET	`1,6`
	FORMULA	`a(n)=2^r, where r is the number of prime factors in the largest unitary square(or square root) divisor of central binomial coefficient: r=A001221[A000188(A001405(n))/A055229(A001405(n))]`
	EXAMPLE	`n=28, binomial[28,14]=2.2.2.3.3.3.5.5.17.19.23. Its has 384 divisors of which 8 are also square numbers: {1,4,9,25,36,100,225,900}. Only {1,25} are also unitary divisors. Thus a(28)=2.`
	CROSSREFS	`A000188, A001405, A055229, A056056, A056057, A056059, A056061, A008833, A034444.` `Sequence in context: A136788 A136450 A131054 this_sequence A056061 A029265 A103648` `Adjacent sequences: A056645 A056646 A056647 this_sequence A056649 A056650 A056651`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), Aug 09 2000`

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Last modified August 28 22:44 EDT 2008. Contains 143251 sequences.

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