write a c program an Arithmetic Progression series sum.

#include<stdio.h>
#include<conio.h>
  main()
{
  int i,n,d,a,tn,sum=0;
  clrscr();
  printf("\n enter the first term of the A.P.");
  scanf("\n %d",&a);
  printf("\n enter the difference of A.P.");
  scanf("\n %d",&d);
  printf("\n enter the total term in A.P.");
  scanf("\n %d",&n);
  sum=(n*(2*a+(n-1)*d))/2;
  tn=a+(n-1)*d;
  printf("\n sum of series =");
  for(i=a;i<=tn;i=i+d);
{
  if(i!=tn)
{
  printf("%d+",i);
}
  else
{
  printf("\n %d=%d",i,sum);
}
}
return (0);
}

output:-
first term of A.P. is  a=3

difference of A.P.is d=5
total term of A.P. is n=5
sum of the series= 3+8+13+18+23=65