arithmomania
noun
arith·mo·ma·nia
| \ ə-ˌrith-mō-ˈmā-nē-ə, -nyə
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Medical Definition of arithmomania
: an abnormal compulsion to count objects or actions and make mathematical calculations
… one finds that this arithmomania is, as it were, the surface of a more fundamental compulsion, which has to do with order and disorder: the need to order, disorder, reorder; the contemplation of order, disorder, new order. Arithmomania has to do with arithmetical order …— Oliver Sacks, Awakenings, 1990