Yes, Dobereiner's triads also exist in the columns of Newlands' octaves.

According to Newland’s law of octaves, every eighth element had properties similar to that of the first. For example: the elements lithium (Li), sodium (Na) and potassium (K) are present in the second column of Newlands' classification of elements. If we consider lithium as the first element, the 8^th element from it will be sodium. Again, considering sodium as the 1^st element, the 8^th element from it is potassium. This means that according to the Newland’s law of octaves, lithium, sodium and potassium should have similar properties. We also know that lithium, sodium and potassium form a Dobereiner's triad having similar chemical properties. This shows that Dobereiner's triads also exist in the columns of Newlands' octaves.