[apps/sequence] Cap the sum of terms to a maximum number of terms

Change-Id: Ib9abcdc92cef5e4e188a81c319b20be2c8b7ab72

apps/sequence/sequence.cpp

@@ -274,6 +274,9 @@ float Sequence::evaluateAtAbscissa(float x, Poincare::Context * context) const {
 
 float Sequence::sumOfTermsBetweenAbscissa(float start, float end, Context * context) {
   float result = 0.0f;
+  if (end-start > k_maxNumberOfTermsInSum) {
+    return NAN;
+  }
   for (float i = roundf(start); i <= roundf(end); i = i + 1.0f) {
     result += evaluateAtAbscissa(i, context);
   }