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A138007 Produced by a sieve: Start with the natural numbers; at the k-th step remove every A138008(k+1)-th term of the sequence remaining after the (k-1)-st sieving step. 2

%I

%S 1,2,4,5,8,10,11,13,17,19,20,23,26,28,31,34,38,40,43,46,47,50,55,56,

%T 58,61,64,68,71,76,77,80,85,86,92,94,95,98,101,103,106,109,115,118,

%U 122,124,125,128,137

%N Produced by a sieve: Start with the natural numbers; at the k-th step remove every A138008(k+1)-th term of the sequence remaining after the (k-1)-st sieving step.

%C The sequence A138008 is defined using this sequence, in the same way as A138008 is used to define this sequence.

%C The sequences can be found this way:

%C Define a(n,1)=n.

%C Now write the natural numbers and run this sieve: In the k-th step remove every a(k+1,1)-th number that remained after k-1 step. You will get this:

%C 1, 3, 7, 13, 19, ... (A000960).

%C Now let a(n,2) be n-th number in this sequence.

%C In the same way: Define a(n,i+1) to be the n-th number left after running the similar sieve on the natural numbers using a(n,i) instead of a(n,1). Now:

%C a(n,2i+1)-> A138007(n) when i->infinity and,

%C a(n,2i)-> A138008(n) when i->infinity.

%e Start with the natural numbers:

%e 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, ...

%e Remove every A138008(2)=3rd term:

%e 1, 2, 4, 5, 7, 8, 10, 11, 13, 14, 16, 17, 19, 20, ...

%e Remove every A138008(3)=5th term:

%e 1, 2, 4, 5, 8, 10, 11, 13, 16, 17, 19, 20, ...

%e Remove every A138008(4)=9th term:

%e 1, 2, 4, 5, 8, 10, 11, 13, 17, 19, 20, ...

%e and so on.

%Y Cf. A138008.

%K nonn

%O 1,2

%A Sune Kristian Jakobsen (sunejakobsen(AT)hotmail.com), Feb 27 2008

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Last modified November 20 05:07 EST 2019. Contains 329323 sequences. (Running on oeis4.)