id:A070807 - OEIS Search Results

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Composite numbers n such that Cototient(totient(n))=A070556(n) is power of 2.

+0
3

4, 6, 8, 9, 10, 12, 14, 15, 16, 18, 20, 21, 24, 26, 28, 30, 32, 34, 35, 36, 39, 40, 42, 45, 48, 51, 52, 56, 58, 60, 64, 65, 68, 70, 72, 78, 80, 84, 85, 87, 90, 96, 102, 104, 105, 112, 116, 119, 120, 128, 130, 136, 140, 144, 145, 153, 156, 160, 168, 170, 174, 180, 192 (list; graph; listen)

	OFFSET	`1,1`
	EXAMPLE	`n=87=3.29:phi[87]=56,56-phi[56]=56-24=32`
	MATHEMATICA	`Do[s= EulerPhi[n]-EulerPhi[EulerPhi[n]]; If[IntegerQ[Log[2, s]]&&!PrimeQ[n], Print[n]], {n, 1, 10000000}]`
	CROSSREFS	`Cf. A070556, A051953, A054571, A070806, A070809-A070811.` `Sequence in context: A115683 A091212 A077094 this_sequence A046352 A046355 A163122` `Adjacent sequences: A070804 A070805 A070806 this_sequence A070808 A070809 A070810`
	KEYWORD	`nonn`
	AUTHOR	`Labos E. (labos(AT)ana.sote.hu), May 08 2002`

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Last modified December 15 00:47 EST 2009. Contains 170825 sequences.

AT&T Labs Research