Template:Sequence of the Day for May 7

Intended for: May 7, 2013

Timetable

• First draft entered by Alonso del Arte on March 22, 2012 ✓
• Draft to be reviewed by March 7, 2013
• Draft to be approved by April 7, 2013

Yesterday's SOTD * Tomorrow's SOTD

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A007535: Smallest pseudoprime

m

greater than

n

to base

n

: smallest composite number

m   >   n

such that

n m  − 1  −  1

is divisible by

m

.

{ 4, 341, 91, 15, 124, 35, 25, 9, 28, ... }

Here the term “pseudoprime” is derived from Fermat's little theorem (see Fermat pseudoprimes): prime numbers satisfy the specified congruence for any coprime base, but these composite numbers satisfy it for a specific base (and possibly others as well)—and hence the theorem provides a useful but not conclusive test of primality.