id:A072963 - OEIS Search Results

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In prime factorization of n replace all single (i.e. non-twin) primes by 1.

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1, 1, 3, 1, 5, 3, 7, 1, 9, 5, 11, 3, 13, 7, 15, 1, 17, 9, 19, 5, 21, 11, 1, 3, 25, 13, 27, 7, 29, 15, 31, 1, 33, 17, 35, 9, 1, 19, 39, 5, 41, 21, 43, 11, 45, 1, 1, 3, 49, 25, 51, 13, 1, 27, 55, 7, 57, 29, 59, 15, 61, 31, 63, 1, 65, 33, 1, 17, 3, 35, 71, 9, 73, 1, 75, 19, 77, 39, 1, 5, 81 (list; graph; listen)

	OFFSET	`1,3`
	COMMENT	`a(a(n)) = a(n).`
	FORMULA	`Multiplicative with a(p) = (if p+2 or p-2 is prime then p else 1), p prime.`
	EXAMPLE	`a(92) = a(2223) = 1; a(93) = a(331) = 331 = 93.`
	CROSSREFS	`Cf. A007510, A000040.` `Sequence in context: A036233 A145799 A098985 this_sequence A161955 A000265 A106617` `Adjacent sequences: A072960 A072961 A072962 this_sequence A072964 A072965 A072966`
	KEYWORD	`nonn,mult`
	AUTHOR	`Reinhard Zumkeller (reinhard.zumkeller(AT)gmail.com), Aug 20 2002`

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Last modified November 24 23:16 EST 2009. Contains 167481 sequences.

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