id:A057023 - OEIS Search Results

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Largest odd factor of (n-th prime-1); k when n-th prime is written as k*2^m+1 [with k odd].

+0
6

1, 1, 1, 3, 5, 3, 1, 9, 11, 7, 15, 9, 5, 21, 23, 13, 29, 15, 33, 35, 9, 39, 41, 11, 3, 25, 51, 53, 27, 7, 63, 65, 17, 69, 37, 75, 39, 81, 83, 43, 89, 45, 95, 3, 49, 99, 105, 111, 113, 57, 29, 119, 15, 125, 1, 131, 67, 135, 69, 35, 141, 73, 153, 155, 39, 79, 165, 21, 173, 87 (list; graph; listen)

	OFFSET	`1,4`
	LINKS	`Index entries for sequences of n such that k2^n-1 (or k2^n+1) is prime`
	FORMULA	`a(n) =A000265(A000040(n)-1)) =A000265(A006093(n)) =(A000040(n)-1)/A007814(A000040(n)-1) =A006093(n)/A023506(n)`
	EXAMPLE	`a(5)=5 because 5th prime is 11 and 11=5*2^1+1`
	CROSSREFS	`Cf. A057024.` `Sequence in context: A103728 A023505 A021743 this_sequence A085849 A100481 A101778` `Adjacent sequences: A057020 A057021 A057022 this_sequence A057024 A057025 A057026`
	KEYWORD	`nonn`
	AUTHOR	`Henry Bottomley (se16(AT)btinternet.com), Jul 24 2000`

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Last modified September 5 01:44 EDT 2008. Contains 143476 sequences.

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