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A214071
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Least m>0 such that 2^n-m and n-m are relatively prime.
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2
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1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 2, 5, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 3, 3, 5, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 1, 1, 1, 1, 3, 1, 3, 1, 1, 2
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OFFSET
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1,4
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LINKS
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EXAMPLE
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gcd(15,3) = 3, gcd(14,2) = 2, gcd(13,1) = 1, so that a(4) = 3.
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MATHEMATICA
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b[n_] := 2^n; c[n_] := n;
Table[m = 1; While[GCD[b[n] - m, c[n] - m] != 1, m++]; m, {n, 1, 140}]
rp[n_]:=Module[{m=1, n2=2^n}, While[!CoprimeQ[n2-m, n-m], m++]; m]; Array[ rp, 100] (* Harvey P. Dale, Feb 13 2021 *)
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CROSSREFS
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KEYWORD
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nonn,easy
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AUTHOR
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STATUS
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approved
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