Feit-Thompson Conjecture
Concerns Primes 
and 
for which 
and 
have a common factor. The only 
pair with bothvalues less than 400,000 is (17, 3313), with a common factor 112,643.
References
Wells, D. G. The Penguin Dictionary of Curious and Interesting Numbers. London: Penguin, p. 17, 1986.
- Subordinate Norm
- Subscript
- Subsequence
- Subset
- Subspace
- Substitution Group
- Substitution Map
- Subtend
- Subtraction
- Succeeds
- Successes
- Sufficient
- Suitable Number
- Sum
- Summand
- Summatory Function
- Sum-Product Number
- Sum Rule
- Sup
- Characteristic (Partial Differential Equation)
- Characteristic Polynomial
- Characteristic (Real Number)
- Character (Multiplicative)
- Character (Number Theory)
- Character Table