Here in the original manuscript, Oliver Cowdery initially wrote the conjunctive appositive (which nonrestrictively postmodifies the Lord God ) with only one and: “the God of Abraham / the God of Isaac / and the God of Jacob”. Later, perhaps when he read the text back to Joseph Smith, Oliver supralinearly inserted an ampersand before “the God of Isaac”. This insertion is written with slightly weaker ink flow. But when Oliver came to copying this conjunctive expression into 𝓟, he once more omitted the first and. And this time he did not correct his error. The printed editions have followed the reading in 𝓟 without the first and.
The exact same sequence of errors and correction is found in 𝓞 for 1 Nephi 17:40; there Oliver Cowdery initially wrote “yea even Abraham Isaac and Jacob”. Later he supralinearly inserted an ampersand before Isaac, but in this case with very weak ink flow. When copying from 𝓞 into 𝓟, Oliver once more omitted the and; and the printed editions have followed the 𝓟 reading. As discussed under 1 Nephi 17:40, the first and in conjuncts involving Abraham, Isaac, and Jacob is optional. Also see the extensive discussion under 1 Nephi 19:10 for the question of how much conjunctive repetition occurs with these three names. The evidence there shows that in each case the critical text should follow the earliest textual sources. Here in Alma 29:11, the critical text will restore the omitted and.
Summary: Restore in Alma 29:11 the corrected reading in 𝓞, which has an and between each instance of “the God of X” (thus “the God of Abraham and the God of Isaac and the God of Jacob”).