Fermat number
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In mathematics, a Fermat number, named after Pierre de Fermat, the first known to have studied them, is a positive integer of the form
where n is a non-negative integer. The first few Fermat numbers are:
3, 5, 17, 257, 65537, 4294967297,... Wikipedia
Conjectured no. of terms: 5
First terms: 3, 5, 17, 257, 65537
Largest known term: 65537
Named after: Pierre de Fermat
OEIS index: A019434