id:A073078 - OEIS Search Results

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Least k such that n divides C(2k,k).

+0
2

1, 1, 2, 3, 3, 2, 4, 7, 5, 3, 6, 5, 7, 4, 8, 15, 9, 5, 10, 3, 5, 6, 12, 7, 13, 7, 14, 5, 15, 8, 16, 31, 6, 9, 4, 5, 19, 10, 7, 13, 21, 5, 22, 6, 8, 12, 24, 15, 25, 13, 11, 7, 27, 14, 8, 11, 11, 15, 30, 14, 31, 16, 5, 63, 8, 6, 34, 9, 14, 4, 36, 14, 37, 19, 14, 10, 6, 7, 40, 15, 41, 21 (list; graph; listen)

	OFFSET	`1,3`
	FORMULA	`a(2^k)=2^k-1, if n is an odd prime a(n)=(n+1)/2 (but there are also some composite satisfying this property),`
	PROGRAM	`(PARI) a(n)=if(n<0, 0, s=1; while(binomial(2*s, s)%n>0, s++); s)`
	CROSSREFS	`Adjacent sequences: A073075 A073076 A073077 this_sequence A073079 A073080 A073081` `Sequence in context: A076742 A036465 A131469 this_sequence A034799 A008985 A138652`
	KEYWORD	`easy,nonn`
	AUTHOR	`Benoit Cloitre (benoit7848c(AT)orange.fr), Aug 17 2002`

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Last modified October 7 14:39 EDT 2008. Contains 144666 sequences.

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