👉 The term "thirteenfold" refers to a mathematical concept where the sum of an arithmetic progression is equal to three times its first term. This can be represented as: a + (n-1)d = 3(a) where: - a is the first term, - n is the number of terms in the sequence, - d is the common difference between each term. To find the value of "d", we need to solve for it, which involves subtracting the last term from
