Sum of arithmetic progression

The program needs to compute the sum of
values of that sequence. remember that an arithmetic progression with initial value a1 and ratio r is
the sequence formed by: a1, a1 + r, a1 + 2r, ···, a1 + (n - 1) r.

Loops/sum.c

@@ -0,0 +1,33 @@
+#include <stdio.h>
+
+ int main(){
+  int a1,r,ne, nf,v,vt,ri;
+  scanf("%d %d %d",&a1,&r,&ne);
+  v = 0;
+  nf = 0;
+  ri=r;
+    for (nf; nf<=ne; nf++){
+        if(nf<ne){
+            v = a1+r;
+            r=r+r;
+            printf("%d\n",v);
+
+    }  
+ }
+  return 0;
+ }
+ */
+    example
+
+    input
+    2 4 5
+    out
+    50
+    --------
+    input
+    7 -2 20
+    out
+    -20
+
+
+ /*