Programming

Hello,
The formula in this problem look like this: Un 1 = [ 29 Un ] - [ n * -50 ] = Un (29 50*n) (formula 1).
We know from school studies that the formula for any element of arithmetic progression is An=A1 (n-1)*d (where A1 - first element and d - difference of arithmetic progression) or An 1=An d (formula 2).
Formulas 1 and 2 are different because in (formula 1) d is a function of n and in (formula 2) d is a constant. So this problem is not about arithmetic progression. Correct me if I am wrong.
Regards,
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