Complete the recursive formula of the arithmetic sequence 13,6,−1,−8,...13,6,−1,−8,...13, comma, 6, comma, minus, 1, comma, minus, 8, comma, point, point, point. C(1)=c(1)=c, left parenthesis, 1, right parenthesis, equals c(n)=c(n−1)+c(n)=c(n−1)+c, left parenthesis, n, right parenthesis, equals, c, left parenthesis, n, minus, 1, right parenthesis, plus