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A329815
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Number of distinct terms in the first difference sequence of the reduced residue system of the n-th primorial.
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2
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0, 1, 3, 5, 7, 10, 13, 16, 20, 23, 29, 33, 37, 43, 49, 53, 59, 66, 75, 84, 92, 99, 108, 116, 127, 132, 140, 148, 156, 164, 174, 185, 193, 206, 215, 224, 235, 245, 255, 267, 275, 286, 297, 308
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OFFSET
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1,3
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COMMENTS
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This sequence is the number of distinct terms in the first difference sequence for rows n in A286941 and A309497.
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LINKS
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FORMULA
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EXAMPLE
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For n = 3, A002110(3) = 30, RRS = {1, 7, 11, 13, 17, 19, 23, 29}, dRRS = {6, 4, 2, 4, 2, 4, 6}, so a(3) = 3.
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MATHEMATICA
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Primorial[n_] := Times @@ Prime[Range[n]]; Table[Length@ Union@ Differences@ Select[Range@ Primorial[n], CoprimeQ[#, Primorial[n]] &], {n, 7}] (* after Michael De Vlieger Jul 15 2017 from A061498 *)
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PROG
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(PARI) f(n) = {my(va = select(x->(gcd(n, x)==1), [1..n])); vd = vector(#va-1, k, va[k+1] - va[k]); #Set(vd); } \\ A061498
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CROSSREFS
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KEYWORD
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nonn,hard
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AUTHOR
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EXTENSIONS
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a(12)-a(44) from Jamie Morken, Jul 11 2020 (after Mario Ziller)
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STATUS
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approved
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