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A026420 a(n) = least positive integer > a(n-1) and not a(i)*a(j) for 1<=i<j<=n. 2

%I #8 Mar 07 2016 08:32:17

%S 2,4,5,6,7,9,11,13,15,16,17,19,21,23,25,27,29,31,33,37,39,40,41,43,47,

%T 48,49,51,53,56,57,59,61,67,69,70,71,72,73,79,81,83,87,88,89,93,97,

%U 101,103,104,107,109,110,111,113,120,121,123,127

%N a(n) = least positive integer > a(n-1) and not a(i)*a(j) for 1<=i<j<=n.

%H Ivan Neretin, <a href="/A026420/b026420.txt">Table of n, a(n) for n = 1..1000</a>

%t a = {2, 4}; used = {a[[1]]*a[[2]]}; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; used = Union[used, k*a]; AppendTo[a, k], {n, 3, 60}]; a (* _Ivan Neretin_, Mar 07 2016 *)

%Y Cf. A026416 and references therein.

%K nonn

%O 1,1

%A _Clark Kimberling_

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