A026445 - OEIS

%I #16 Feb 07 2025 22:46:30

%S 2,3,4,5,6,7,9,11,13,15,18,19,21,25,27,31,33,34,36,39,42,43,45,48,49,

%T 50,51,53,55,58,60,61,63,66,69,71,72,73,75,76,81,82,84,85,87,89,90,91,

%U 94,96,99,103,105,106,109,111,113,114,115,117

%N a(n) = least positive integer > a(n-1) and not a(i)*a(j)+2 for 1<=i<j<=n, with initial terms 2,3.

%H Ivan Neretin, <a href="/A026445/b026445.txt">Table of n, a(n) for n = 1..1000</a>

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

%Y Cf. A026443 and references therein.

%K nonn,changed

%O 1,1

%A _Clark Kimberling_

%E Name clarified by _Robert C. Lyons_, Feb 07 2025