id:A090544 - OEIS Search Results

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Let f(k) = k + pi(k); a(n) = least number of steps for f(f(f(...(n)))) to reach a prime.

+0
3

1, 1, 3, 3, 2, 1, 2, 1, 4, 6, 1, 1, 3, 2, 5, 8, 4, 3, 2, 1, 4, 2, 7, 3, 10, 2, 1, 5, 3, 3, 1, 6, 2, 9, 1, 5, 3, 4, 2, 3, 2, 2, 5, 1, 8, 9, 3, 4, 2, 3, 1, 12, 2, 1, 10, 1, 4, 2, 7, 1, 8, 2, 3, 1, 2, 2, 3, 11, 1, 4, 9, 24, 3, 5, 1, 6, 18, 1, 7, 1, 2, 10, 1, 6, 1, 2, 10, 1, 8, 3, 8, 3, 23, 2, 4, 12, 5, 17, 3, 1, 6 (list; graph; listen)

	OFFSET	`2,3`
	EXAMPLE	`a(4) = 3, f(4) = 4+2 = 6, f(6) = 6+3 = 9, f(9)= 9+4 = 13 is prime.` `a(10) = 4, f(10) = 10+4=14, f(14) = 14+6 = 20, f(20) = 20+8 = 28, f(28) = 28+9 = 37.`
	CROSSREFS	`Cf. A090545, A090546.` `Sequence in context: A016455 A060574 A075522 this_sequence A038766 A080993 A140259` `Adjacent sequences: A090541 A090542 A090543 this_sequence A090545 A090546 A090547`
	KEYWORD	`nonn`
	AUTHOR	`Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Dec 09 2003`
	EXTENSIONS	`More terms from Frank Adams-Watters (FrankTAW(AT)Netscape.net), Apr 26 2006`

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Last modified July 24 12:00 EDT 2008. Contains 142294 sequences.

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