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A026448 a(n) = least positive integer > a(n-1) and not a(i)*a(j)+2 for i<=1<=j<=n. 2

%I

%S 1,2,5,8,9,13,14,17,21,22,25,26,29,32,33,37,38,41,45,48,49,53,56,57,

%T 61,62,65,69,70,73,77,80,81,85,86,89,90,93,94,97,101,102,105,109,110,

%U 113,117,118,121,122,125,129,130,133,134,137,141

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

%H Ivan Neretin, <a href="/A026448/b026448.txt">Table of n, a(n) for n = 1..1000</a>

%t a = {1, 2}; used = {a[[1]]^2 + 2, a[[1]]*a[[2]] + 2, a[[2]]^2 + 2}; Do[k = a[[-1]] + 1; While[MemberQ[used, k], k++]; AppendTo[a, k]; used = Union[used, k*a + 2], {n, 3, 60}]; a (* _Ivan Neretin_, Mar 06 2016 *)

%Y Cf. A026443 and references therein.

%K nonn

%O 1,2

%A _Clark Kimberling_

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Last modified February 25 08:33 EST 2021. Contains 341606 sequences. (Running on oeis4.)