Fermat Numbers
Fn = 22n + 1 for n ≥ 0
{\displaystyle F_{n}=2^{2^{n}}+1,},{\displaystyle F_{n}=2^{2^{n}}+1,},{\displaystyle F_{n}=2^{2^{n}}+1,},{\displaystyle F_{n}=2^{2^{n}}+1,},{\displaystyle F_{n}=2^{2^{n}}+1,},{\displaystyle F_{n}=2^{2^{n}}+1,},{\displaystyle F_{n}=2^{2^{n}}+1,}
3
5
17
257
65537
4294967297
18446744073709551617
…