id:A071578 - OEIS Search Results

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Number of iterations of Pi(n) needed to reach 1, where Pi(x) denotes the number of primes <= x.

+0
1

0, 1, 2, 2, 3, 3, 3, 3, 3, 3, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 4, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5, 5 (list; graph; listen)

	OFFSET	`1,3`
	FORMULA	`a(n) = a(Pi(n))+1.`
	PROGRAM	`(PARI) for(n=2, 150, s=n; t=0; while(s!=1, t++; s=sum(i=2, s, isprime(i)); if(s==1, print1(t, ", "); ); ))`
	CROSSREFS	`Cf. A000720.` `Sequence in context: A077463 A084556 A084506 this_sequence A157791 A156874 A078767` `Adjacent sequences: A071575 A071576 A071577 this_sequence A071579 A071580 A071581`
	KEYWORD	`easy,nonn`
	AUTHOR	`Benoit Cloitre (benoit7848c(AT)orange.fr), May 31 2002`

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Last modified December 11 12:57 EST 2009. Contains 170656 sequences.

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