The following table is given as a numerical representation of Gen. 5:3-31. The Moses version of this genealogy, which continues all the way to Moses 8:12, does not alter the ages of the Patriarchs. The numbers are the same.
If the Fall of Adam occurred at 4000 BC (a common hypothesis), then the chronology of these patriarchs can be calculated. Section 107 of the D&C also gives this same chronology but focuses not on the son’s age at birth but rather his age at ordination to the priesthood. Often referred to as the Patriarchal priesthood, the name of the priesthood was changed to Melchizedek after the Flood.
While we might assume that the priesthood was administered strictly in a father to son fashion, this was not the case. Adam was still alive even when Lamech was born. Section 107 explains that Adam ordained Seth, Enos, Cainan, Mahalaleel, Jared, Enoch, and Methuselah at various ages and places (DC 107:41-52). Lamech was not ordained by his father but by Seth.