id:A073756 - OEIS Search Results

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Number of steps needed to reach a prime when the following map is repeatedly applied to n: if n is even then 2n + int(ln(n)) + 1, otherwise 2n - int(ln(n)) - 1; or -1 if no prime is ever reached.

+0
6

1, 3, 2, 2, 2, 19, 1, 19, 1, 1, 18, 1, 1, 18, 3, 1, 12, 3, 1, 9, 15, 3, 8, 3, 3, 17, 77, 3, 5, 6, 3, 9, 2, 2, 2, 31, 8, 11, 2, 5, 2, 11, 69, 34, 2, 17, 14, 2, 16, 33, 7, 8, 2, 14, 2, 1, 5, 1, 76, 2, 8, 5, 4, 76, 1, 8, 2, 4, 30, 1, 1, 2, 10, 30, 1, 1, 4, 10, 7, 1, 10, 4, 1, 7, 33, 10, 1, 1, 16, 33 (list; graph; listen)

	OFFSET	`2,2`
	PROGRAM	`10 cls 30 for I=2 to 100 32 H=I 40 if odd(H)=1 then goto 90 else goto 50 50 A=2H+int(log(H))+1:K=K+1 60 if prmdiv(A)=A then print I, K:goto 120 65 if K>1000 then print I, 0:goto 120 70 H=A:goto 40 90 A=2H-int(log(H))-1:K=K+1 100 if prmdiv(A)=A then print I, K:goto 120 105 if K>1000 then print I, 0:goto 120 110 H=A:goto 40 120 K=0 130 next`
	CROSSREFS	`Sequence in context: A090207 A065437 A097721 this_sequence A006379 A105198 A133882` `Adjacent sequences: A073753 A073754 A073755 this_sequence A073757 A073758 A073759`
	KEYWORD	`easy,nonn`
	AUTHOR	`Felice Russo (felice.russo(AT)katamail.com), Sep 02 2002`

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Last modified November 27 14:50 EST 2009. Contains 167570 sequences.

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