A374134 - OEIS

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A374134

a(n) = 1 if 2*phi(n) > n, otherwise 0, where phi is Euler's totient function phi, A000010.

1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 0, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1 (list; graph; refs; listen; history; text; internal format)

	OFFSET	`1`
	LINKS	`Antti Karttunen, Table of n, a(n) for n = 1..100000` `Index entries for characteristic functions`
	FORMULA	`a(n) = [A083254(n) > 0], where [ ] is the Iverson bracket.` `a(2*k) = 0 for k >= 1. - Paolo Xausa, Jul 08 2024`
	MATHEMATICA	`Array[Boole[2EulerPhi[#] > #] &, 100] ( Paolo Xausa, Jul 08 2024 *)`
	PROG	`(PARI) A374134(n) = ((2*eulerphi(n))>n);`
	CROSSREFS	`Characteristic function of A089684.` `Cf. A000010, A083254, A318874 (inverse Möbius transform), A323170.` `Differs from A000035 first at n=105, where a(105) = 0, while A000035(105) = 1.` `Differs from A374136 first at n=255, where a(255) = 1, while A374136(255) = 0.` `Sequence in context: A059841 A056594 A101455 * A374136 A091337 A166698` `Adjacent sequences: A374131 A374132 A374133 * A374135 A374136 A374137`
	KEYWORD	`nonn,new`
	AUTHOR	`Antti Karttunen, Jul 06 2024`
	STATUS	`approved`

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Last modified July 18 18:59 EDT 2024. Contains 374388 sequences. (Running on oeis4.)