In a related sequence, the first 5 terms in the sequence of Catalan–Mersenne numbers 
  
    
      
        
          M
          
            
              c
              
                n
              
            
          
        
      
    
    {\displaystyle M_{c_{n}}}
   are the only known prime terms, with a sixth possible candidate in the order of 101037.7094. These prime sequences are conjectured to be prime up to a certain limit.
Tympanosclerosis is a condition caused by hyalinization and subsequent calcification of subepithelial connective tissue of the tympanic membrane and middle ear, sometimes resulting in a detrimental effect to hearing. Signs and symptoms
Myringosclerosis rarely causes any symptoms. Tympanosclerosis, on the other hand, can cause significant hearing loss or chalky, white patches on the middle ear or tympanic membrane. Causes
The aetiology for tympanosclerosis is not extensively understood. There are several probable factors which could result in the condition appearing, including:

Long term otitis media (or glue ear)
Insertion of a tympanostomy tube. If aspiration is performed as part of the insertion, the risk of tympanosclerosis occurring increases. Risk also increases if a larger tube is used, or if the procedure is repeated. Atherosclerosis
There is ongoing research as to whether or not cholesteatoma is associated with tympanosclerosis. If there is an association, it is likely that the two conditions co-exist. Pathophysiology
Increased fibroblast activity results in deposition of collagen. Calcium phosphate plaques then form in the lamina propria of the tympanic membrane. Diagnosis
If lesions are typical, non-extensive and with no detriment to hearing, investigation into the condition is rarely required. Audiometry is used to determine the extent of hearing loss, if any. Tympanometry produces tympanograms which can be different when tympanosclerosis is present. Computerised tomography (CT) can be used to determine if disease is present in the middle ear.