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Search: id:A118501
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| A118501 |
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A variation on Flavius's sieves (A099204, A099243): Start with the Chen numbers; at the k-th sieving step, remove every p-th term of the sequence remaining after the (k-1)-st sieving step, where p is the k-th prime; iterate. |
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| 2, 5, 17, 23, 53, 83, 127, 167, 181, 211, 281, 347, 449, 467, 499, 509, 641, 677, 821, 887, 941, 953, 1097, 1193, 1283, 1327, 1399, 1471, 1583, 1721, 1949, 2029, 2111, 2213, 2351, 2381, 2447, 2549, 2609, 2777, 3061, 3137, 3257, 3307, 3511, 3539, 3797
(list; graph; listen)
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OFFSET
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1,1
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EXAMPLE
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Start with
2 3 5 7 11 13 17 19 23 29 31 37 41 47 53 59 67 71 83 89 101 107 109 113 127 131 ... and delete every second term, giving
2 5 11 17 23 31 41 53 67 83 101 109 127 ... and delete every 3rd term, giving
2 5 17 23 41 53 83 101 127 ... and delete every 5th term, giving
2 5 17 23 53 83 101 127
.... Continue for ever, and what's left is the sequence.
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MAPLE
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ts_chen:= proc(n) local i, ans; ans:=[ ]: for i from 1 to n do if ( isprime(i) = 'true') then if ( isprime(i+2) = 'true' or numtheory[bigomega](i+2) = 2) then ans:=[ op(ans), i ] fi fi od: return ans end: S[1]:=convert(ts_chen(25000), set): for n from 2 to 390 do S[n]:=S[n-1] minus {seq(S[n-1][ithprime(n-1)*i], i=1..nops(S[n-1])/ithprime(n-1))} od: convert(S[390], list);
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CROSSREFS
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Cf. A099204, A099243, A109611.
Sequence in context: A106021 A032605 A099243 this_sequence A023244 A023867 A024594
Adjacent sequences: A118498 A118499 A118500 this_sequence A118502 A118503 A118504
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KEYWORD
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nonn
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AUTHOR
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Jani Melik (jani_melik(AT)hotmail.com), May 05 2006
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