How to display the first ten series: 1,--3,5,-7,9,.............

Question

The first term of the series must be positive and then negative and then positive and then so on.

Answer 1

Like this?

for (int i = 1, count = 0; count < 10; i+=2) {
System.out.print((count % 2 == 0 ? "" : "-") + i + " ");
count++;
}

Answer 2

(-1)**(n%2)*(2*n+1)

Answer 3

Hint: The nth element of the series is equal to a_{n-1}+4*n*(-1)^n