int catalan_number ( int n );
int i4_factorial ( int n );
void matrix_chain_brute ( int n_mats, int dims[], int *cost, int p[] );
bool pivot_sequence_check ( int n, int t[] );
int pivot_sequence_enum ( int n );
void pivot_sequence_successor ( int n, int t[] );
void pivot_sequence_to_matrix_chain_cost ( int n_mats, int p[], int dims[],
  int *cost );