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 A071222 Smallest k such that gcd(n,k) = gcd(n+1,k+1). 8
 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 6, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2, 1, 4, 1, 2, 1, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS a(n) = least m>0 such that gcd(n!+1+m,n-m) = 1.  [Clark Kimberling, Jul 21 2012] From Antti Karttunen, Jan 26 2014: (Start) a(n-1)+1 = A053669(n) = Smallest k >= 2 coprime to n = Smallest prime not dividing n. Note that a(n) is equal to A235918(n+1) for the first 209 values of n. The first difference occurs at n=210 and A235921 lists the integers n for which a(n) differs from A235918(n+1). (End) LINKS Clark Kimberling & Antti Karttunen, Table of n, a(n) for n = 0..10001 (Terms up to n=1000 from Kimberling) MATHEMATICA sgcd[n_]:=Module[{k=1}, While[GCD[n, k]!=GCD[n+1, k+1], k++]; k]; Array[sgcd, 110] (* Harvey P. Dale, Jul 13 2012 *) PROG (PARI) for(n=1, 140, s=1; while(gcd(s, n)

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Last modified February 25 04:32 EST 2020. Contains 332217 sequences. (Running on oeis4.)