Matlab, 69 bytes

i=1;a=[];while 1;if all(a~=i);disp(i);a=[a [2 3 4 9]*i];end;i=i+1;end

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It basically is a translation of pxeger's answer. Matlab also has a union function, but it would cost 5 bytes.

Matlab, 69 66 bytes

i=1;a=[];while 1;if all(a-i);disp(i);a=[a [2:4 9]*i];end;i=i+1;end

Try it online!

It basically is a translation of pxeger's answer. Matlab also has a union function, but it would cost 5 bytes.

-3 bytes thanks to Luis Mendo