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Search: id:A074818
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| A074818 |
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Number of integers in {1, 2, ..., prime(n)} that are coprime to n. |
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+0
1
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| 2, 2, 4, 4, 9, 5, 15, 10, 16, 12, 29, 13, 38, 19, 26, 27, 56, 21, 64, 29, 42, 36, 80, 30, 78, 47, 69, 46, 106, 31, 123, 66, 84, 66, 103, 51, 153, 78, 104, 70, 175, 52, 187, 88, 106, 96, 207, 75, 195, 92, 147, 111, 237, 84, 187, 113, 170, 131, 273, 75, 279, 142, 176
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Compare the definition of a(n) to phi(n) = number of integers in {1, 2, ..., n} that are coprime to n.
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EXAMPLE
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There are five numbers in {1, 2, ..., prime(6) = 13} that are coprime to 6, i.e. 1, 5, 7, 11, 13. Hence a(6) = 5.
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MATHEMATICA
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h[n_] := Module[{l}, l = {}; For[i = 1, i <= Prime[n], i++, If[GCD[i, n] == 1, l = Append[l, i]]]; l]; Table[Length[h[i]], {i, 1, 100}]
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CROSSREFS
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Sequence in context: A063776 A118406 A072488 this_sequence A110199 A053656 A035054
Adjacent sequences: A074815 A074816 A074817 this_sequence A074819 A074820 A074821
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KEYWORD
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nonn
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AUTHOR
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Joseph L. Pe (joseph_l_pe(AT)hotmail.com), Oct 04 2002
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