Explanation:
it seems we are dealing with subtraction, as the differences between the 1st and second, and between the 2nd and 3rd numbers are equal : -7
so, we can assume that the sequence is created by always subtracting 7.
a1 = 352
a2 = a1 - 7 = 352 - 7 = 345
a3 = a2 - 7 = a1 - 7 - 7 = 352 - 7 - 7 = 338
an = an-1 - 7 = a1 - 7(n-1) = 352 - 7(n-1)
a43 = 352 - 7(43-1) = 352 - 7×42 = 352 - 294 = 58