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A157419
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a(0)=1. a(n) = the smallest integer coprime to a(n-1) and greater than the n-th prime.
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4
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1, 3, 4, 7, 8, 13, 14, 19, 20, 27, 31, 32, 39, 43, 44, 49, 54, 61, 62, 69, 73, 74, 81, 85, 91, 99, 103, 104, 109, 110, 117, 128, 133, 138, 143, 150, 157, 158, 165, 169, 174, 181, 182, 193, 194, 199, 200, 213, 224, 229, 230, 237, 241, 242, 255, 259, 264, 271, 272, 279
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OFFSET
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0,2
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LINKS
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EXAMPLE
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a(8) = 20, and the 9th prime is 23. So for a(9) we want the smallest integer that is both coprime to 20 and is > 23. Checking: 24 is not coprime to 20. 25 is not coprime to 20. 26 is not coprime to 20. But 27 is coprime to 20, so a(9) = 27.
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MATHEMATICA
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Fold[Append[#1, Block[{k = Prime@ #2 + 1}, While[! CoprimeQ[k, #1[[-1]] ], k++]; k]] &, {1}, Range@ 59] (* Michael De Vlieger, Oct 30 2017 *)
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CROSSREFS
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KEYWORD
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nonn
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AUTHOR
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EXTENSIONS
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STATUS
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approved
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