What do I need to do to get the correct value o PI?

Greeting.
I am doing the following exercise: Run a program to determine an approximate value of π using the series shown below. The calculation is performed by generating a certain number of terms in the series. The number of terms to be considered is read from the standard input (keyboard) (greater than or equal to 30000).
Note: In the resolution of this issue, you cannot use functions from the math.h library of the C programming language.

example: input a value enter total terms >=30000: entering 30000 should give you the result o pi:3.141559
The prolem I’m having: Uppon entering the same value(30000)I am not getting the corret value o pi=3.14…. but instead it’s something like:0.0067…

heres my code:

#include<stdio.h>
#include<math.h>
int main(void){
    double numerator, denominator, pi=0.0;
    int k;
    printf("input a total number o terms >=30000:");
    for ( k=1;k<=30000;k++){
         scanf("%d",&k);

         if(k>=30000){
    
             if(k%2==0){
                 numerator=1;   
             }
             else {
                  numerator=-1;
             }
          }
          denominator=2.0*k+1.0;
          pi+=numerator/denominator;
          pi=4*pi;
          printf("value of PI is= %lf",pi);
    }
return 0;
}

Can someone point out what I am doing wrong and how can I solve it pls?

Your time and attention are deeply appreciated.

Thank You.

>Solution :

There are many problems with what your implementation of the algorithm:

Try avoiding scanf ad printf inside the for loop.

Instead of getting the k variable from the user try and get the maximum value of k.

denominator=2*k+1 is wrong if you follow the algorithm that you gave in your question and should be changed to denominator=2*k-1.

You repeat pi*=4 every iteration.

I applied all those improvement and i get pi=3.141926 for just 3000 iterations.

Here a little help on how your for loop should look like:

for (int k=1;k<iterations;k++){
      numerator*=-1;
      denominator=2.0*k-1.0;
      pi+=numerator/denominator;
}