Republic of Mathematics blog

Archive for May 2011

Spotting patterns and finding explanations: Dijkstra’s fusc function

Posted by: Gary Ernest Davis on: May 18, 2011

Edsger Dijkstra named the integer valued function, fusc, of a non-negative integer variable, as follows: , , and Dijkstra’s writings on fusc can be found at the Edgar W. Dijkstra Archive (EWD 578). The values of fusc can be computed in any decent programming language (one that has a built-in routine for recognizing odd and […]

Catalan pseudo-primes

Posted by: Gary Ernest Davis on: May 16, 2011

Catalan pseudoprimes As a special case of Fermat’s little theorem, if is an odd prime number then is divisible by , or, in the language of congruences, . The converse of this is not true: if where is a positive integer, it does not follow that is prime. For example could be . There are […]