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%I #17 Feb 24 2021 08:21:14
%S 4,6,26,626,34,4762,94,10,59450441556482,37219202,226,14,22,359948158,
%T 141142,957030986,82,926,46,38,86,158,262,1126,
%U 589928909976251551945088438,4486,2434,62,12398,2367240322,2942,10430585378,218,394,122,74,1042,19862,11197742711219732052345406
%N Even semiprime equivalent to the Euclid-Mullin sequence: a(1) = 4, a(n) = smallest semiprime divisor of product of previous terms plus 2.
%C Except for 4, all terms are guaranteed to be squarefree.
%e a(5) = 34 because the previous terms being 4, 6, 26 and 626, their product is 390624, and 390624 + 2 = 2 * 17 * 11489, the least semiprime divisor of which is 2 * 17 = 34.
%t smallestPrimeFactor[n_] := FactorInteger[n][[1, 1]]; semiprimePart[n_] := Module[{p = smallestPrimeFactor[n]}, p*smallestPrimeFactor[n/p]]; a = {4}; Do[AppendTo[a, semiprimePart[2 + Times @@ a]], {15}]; a (* _T. D. Noe_, Aug 02 2011 *)
%Y Cf. A000945, A000946, A100484.
%K nonn
%O 1,1
%A _Alonso del Arte_ and _Jonathan Vos Post_, Aug 02 2011
%E More terms from _Amiram Eldar_, Feb 24 2021