diff --git a/apps/sequence/sequence.cpp b/apps/sequence/sequence.cpp
index 689098ca9..27841a174 100644
--- a/apps/sequence/sequence.cpp
+++ b/apps/sequence/sequence.cpp
@@ -161,4 +161,15 @@ Poincare::ExpressionLayout * Sequence::secondInitialConditionName() {
   return m_secondInitialConditionName;
 }
 
+bool Sequence::isDefined() {
+  switch (m_type) {
+    case Type::Explicite:
+      return layout() != nullptr;
+    case Type::SingleRecurrence:
+      return layout() != nullptr && m_firstInitialConditionLayout != nullptr;
+    default:
+      return layout() != nullptr && m_firstInitialConditionLayout != nullptr && m_secondInitialConditionLayout != nullptr;
+  }
+}
+
 }
diff --git a/apps/sequence/sequence.h b/apps/sequence/sequence.h
index b47ab0e1a..7eeb058d2 100644
--- a/apps/sequence/sequence.h
+++ b/apps/sequence/sequence.h
@@ -29,6 +29,7 @@ public:
   Poincare::ExpressionLayout * definitionName();
   Poincare::ExpressionLayout * firstInitialConditionName();
   Poincare::ExpressionLayout * secondInitialConditionName();
+  bool isDefined() override;
 private:
   Type m_type;
   char m_firstInitialConditionText[Shared::Function::k_bodyLength];
diff --git a/apps/shared/function.cpp b/apps/shared/function.cpp
index c5aa8f341..f4e0d4cba 100644
--- a/apps/shared/function.cpp
+++ b/apps/shared/function.cpp
@@ -62,6 +62,10 @@ Poincare::ExpressionLayout * Function::layout() {
   return m_layout;
 }
 
+bool Function::isDefined() {
+  return m_layout != nullptr;
+}
+
 bool Function::isActive() {
   return m_active;
 }
diff --git a/apps/shared/function.h b/apps/shared/function.h
index 1d9022559..1b19233c2 100644
--- a/apps/shared/function.h
+++ b/apps/shared/function.h
@@ -15,6 +15,7 @@ public:
   KDColor color() const { return m_color; }
   Poincare::Expression * expression();
   Poincare::ExpressionLayout * layout();
+  virtual bool isDefined();
   bool isActive();
   void setActive(bool active);
   void setContent(const char * c);
diff --git a/apps/shared/function_store.cpp b/apps/shared/function_store.cpp
index 2663af258..0c735f7aa 100644
--- a/apps/shared/function_store.cpp
+++ b/apps/shared/function_store.cpp
@@ -12,7 +12,7 @@ Function * FunctionStore::activeFunctionAtIndex(int i) {
   assert(i>=0 && i<m_numberOfFunctions);
   int index = 0;
   for (int k = 0; k < m_numberOfFunctions; k++) {
-    if (functionAtIndex(k)->isActive() && functionAtIndex(k)->layout() != nullptr) {
+    if (functionAtIndex(k)->isActive() && functionAtIndex(k)->isDefined()) {
       if (i == index) {
         return functionAtIndex(k);
       }
@@ -27,7 +27,7 @@ Function * FunctionStore::definedFunctionAtIndex(int i) {
   assert(i>=0 && i<m_numberOfFunctions);
   int index = 0;
   for (int k = 0; k < m_numberOfFunctions; k++) {
-    if (functionAtIndex(k)->layout() != nullptr) {
+    if (functionAtIndex(k)->isDefined()) {
       if (i == index) {
         return functionAtIndex(k);
       }
@@ -45,7 +45,7 @@ int FunctionStore::numberOfFunctions() {
 int FunctionStore::numberOfActiveFunctions() {
   int result = 0;
   for (int i = 0; i < m_numberOfFunctions; i++) {
-    if (functionAtIndex(i)->layout() != nullptr && functionAtIndex(i)->isActive()) {
+    if (functionAtIndex(i)->isDefined() && functionAtIndex(i)->isActive()) {
       result++;
     }
   }
@@ -55,7 +55,7 @@ int FunctionStore::numberOfActiveFunctions() {
 int FunctionStore::numberOfDefinedFunctions() {
   int result = 0;
   for (int i = 0; i < m_numberOfFunctions; i++) {
-    if (functionAtIndex(i)->layout() != nullptr) {
+    if (functionAtIndex(i)->isDefined()) {
       result++;
     }
   }