id:A065556 - OEIS Search Results

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Numbers n such that sigma (phi ( n ) ) = sigma (sigma (n ) ) where phi is Euler's totient and sigma is the multiplicative sum-of-divisors function.

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1, 367, 919, 1967, 3641, 4379, 5143, 7379, 11843, 12767, 13493, 15293, 21797, 26039, 28381, 29807, 30263, 30593, 30599, 30887, 37523, 40199, 48559, 49781, 51101, 51397, 55277, 62573, 67223, 72433, 73979, 87047, 89255, 89851, 95393 (list; graph; listen)

	OFFSET	`1,2`
	FORMULA	`sigma (phi ( n ) ) = sigma (sigma (n ) )`
	EXAMPLE	`367 is in the sequence because phi ( 367 ) = 366, sigma (367 ) = 368, sigma (366 ) = 744 = sigma (368 ).`
	CROSSREFS	`A033632 A000010 A000203` `Adjacent sequences: A065553 A065554 A065555 this_sequence A065557 A065558 A065559` `Sequence in context: A054827 A059230 A060518 this_sequence A068357 A067891 A142579`
	KEYWORD	`nonn`
	AUTHOR	`Walter Nissen (wnissen(AT)tfn.net), Nov 28 2001`

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Last modified October 13 20:18 EDT 2008. Contains 145016 sequences.

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