A100410 - OEIS

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A100410

Numbers n such that n is the phi(n)-th composite number (n=A002808(phi(n)).

6, 15, 21, 265, 295, 2681, 174757, 1302197 (list; graph; refs; listen; history; internal format)

	OFFSET	`1,1`
	COMMENTS	`n is in the sequence iff n=phi(n)+pi(n)+1. Next term is greater than 75000000.`
	EXAMPLE	`15 is in the sequence because phi(15)=8 & 15=A002808(8).`
	MATHEMATICA	`Do[If[n==EulerPhi[n]+PrimePi[n]+1, Print[n]], {n, 75000000}]`
	CROSSREFS	`Cf. A100411, A002808, A037170.` `Sequence in context: A138109 A072521 A130178 * A095032 A187918 A190747` `Adjacent sequences: A100407 A100408 A100409 * A100411 A100412 A100413`
	KEYWORD	`more,nonn`
	AUTHOR	`Farideh Firoozbakht (mymontain(AT)yahoo.com), Dec 01 2004`

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Last modified February 16 14:37 EST 2012. Contains 205930 sequences.