id:A072027 - OEIS Search Results

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A072027

Swap (2,3) and all twin prime pairs >(3,5) in prime factorization of n.

+0
4

1, 3, 2, 9, 7, 6, 5, 27, 4, 21, 13, 18, 11, 15, 14, 81, 19, 12, 17, 63, 10, 39, 23, 54, 49, 33, 8, 45, 31, 42, 29, 243, 26, 57, 35, 36, 37, 51, 22, 189, 43, 30, 41, 117, 28, 69, 47, 162, 25, 147, 38, 99, 53, 24, 91, 135, 34, 93, 61, 126, 59, 87, 20, 729, 77 (list; graph; listen)

	OFFSET	`1,2`
	COMMENT	`a(a(n))=n, self-inverse permutation of natural numbers; a(n)=n for single primes (A007510) and products of twin prime pairs (A037074).`
	LINKS	`Index entries for sequences that are permutations of the natural numbers`
	FORMULA	`Multiplicative with a(p) = (if p<=3 then 5-p else (if p+2 is prime then p+2 else (if p-2 is prime then p-2 else p))), p prime.`
	EXAMPLE	`a(143)=a(1113)=a(11)a(13)=1311=143; a(77)=a(711)=a(7)a(11)=513=65.`
	CROSSREFS	`Cf. A072026, A001359, A006512, A072028, A072029, A061898, A064505.` `Sequence in context: A019778 A134480 A011323 this_sequence A061898 A021756 A084398` `Adjacent sequences: A072024 A072025 A072026 this_sequence A072028 A072029 A072030`
	KEYWORD	`nonn,mult`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)lhsystems.com), Jun 07 2002`

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Last modified August 29 17:54 EDT 2008. Contains 143238 sequences.

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