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A115928 Smallest number which is coprime to the last four predecessors and not occurring earlier; a(1)=1, a(2)=2, a(3)=3 & a(4)=4. 0

%I

%S 1,2,3,4,5,7,9,8,11,13,15,14,17,19,23,6,25,29,31,12,35,37,41,16,21,43,

%T 47,10,27,49,53,20,33,59,61,26,45,67,71,22,39,73,79,28,51,55,83,32,57,

%U 65,77,34,69,89,91,38,75,97,101,44,63,85,103,46,81,195,107,52,87,109,113,40,93,119

%N Smallest number which is coprime to the last four predecessors and not occurring earlier; a(1)=1, a(2)=2, a(3)=3 & a(4)=4.

%t f[s_] := Block[{k = 1, l = Take[s,-4]}, While[ Union[ GCD[k, l]] != {1} || MemberQ[s,k], k++]; Append[s,k]]; Nest[f, {1,2,3,4}, 70]

%Y Cf. A084937, A103683.

%K easy,nonn

%O 1,2

%A _Robert G. Wilson v_, Jun 26 2011

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Last modified January 23 16:48 EST 2020. Contains 331173 sequences. (Running on oeis4.)