Write a program to generate the sequence: –5, 10, –15, 20, –25….. upto n, where n is an integer input by the user.

Question

Accepted Answer

> [!TLDR]
> Spot the pattern — the i-th term is 5 times i, with a minus sign at odd positions — then loop i from 1 to n printing 5*i negated when i is odd.

**The idea: find the term's formula first.** Writing the positions against the terms:

| Position i | 1 | 2 | 3 | 4 | 5 |
| --- | --- | --- | --- | --- | --- |
| Term | -5 | 10 | -15 | 20 | -25 |

The magnitude is always 5 × i; the **sign alternates**, negative when i is odd, positive when i is even. Once the i-th term is expressible from i alone, a simple counted for loop generates the sequence. (We read "upto n" the standard way: **n is the number of terms** the user wants.)

**Program**

```python
n = int(input("Enter the number of terms n: "))

for i in range(1, n + 1):
    term = 5 * i
    if i % 2 == 1:      # odd position -> negative term
        term = -term
    print(term, end=" ")
print()
```

**Sample run**

```text
Enter the number of terms n: 6
-5 10 -15 20 -25 30
```

**Trace for n = 6**

| i | 5 * i | i odd? | term printed |
| --- | --- | --- | --- |
| 1 | 5 | yes | -5 |
| 2 | 10 | no | 10 | …

Q.Write a program to generate the sequence: –5, 10, –15, 20, –25….. upto n, where n is an integer input by the user.

Concept understanding — Iteration With Condition

Iteration With Condition

The Intuition

The Precise Statement

A Concrete Example

Q.Write a program to generate the sequence: –5, 10, –15, 20, –25….. upto n, where n is an integer input by the user.

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