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  2. Catalan number - Wikipedia

    en.wikipedia.org/wiki/Catalan_number

    The only known odd Catalan numbers that do not have last digit 5 are C 0 = 1, C 1 = 1, C 7 = 429, C 31, C 127 and C 255. The odd Catalan numbers, C n for n = 2 k − 1, do not have last digit 5 if n + 1 has a base 5 representation containing 0, 1 and 2 only, except in the least significant place, which could also be a 3. [3]

  3. List of undecidable problems - Wikipedia

    en.wikipedia.org/wiki/List_of_undecidable_problems

    Though undecidable languages are not recursive languages, they may be subsets of Turing recognizable languages: i.e., such undecidable languages may be recursively enumerable. Many, if not most, undecidable problems in mathematics can be posed as word problems : determining when two distinct strings of symbols (encoding some mathematical ...

  4. RE (complexity) - Wikipedia

    en.wikipedia.org/wiki/RE_(complexity)

    The set of recursive languages is a subset of both RE and co-RE. [3] In fact, it is the intersection of those two classes, because we can decide any problem for which there exists a recogniser and also a co-recogniser by simply interleaving them until one obtains a result.

  5. Recursive partitioning - Wikipedia

    en.wikipedia.org/wiki/Recursive_partitioning

    Recursive partitioning is a statistical method for multivariable analysis. [1] Recursive partitioning creates a decision tree that strives to correctly classify members of the population by splitting it into sub-populations based on several dichotomous independent variables .

  6. Computable set - Wikipedia

    en.wikipedia.org/wiki/Computable_set

    In computability theory, a set of natural numbers is called computable, recursive, or decidable if there is an algorithm which takes a number as input, terminates after a finite amount of time (possibly depending on the given number) and correctly decides whether the number belongs to the set or not.

  7. Mutual recursion - Wikipedia

    en.wikipedia.org/wiki/Mutual_recursion

    In mathematics, the Hofstadter Female and Male sequences are an example of a pair of integer sequences defined in a mutually recursive manner. Fractals can be computed (up to a given resolution) by recursive functions. This can sometimes be done more elegantly via mutually recursive functions; the SierpiƄski curve is a good example.

  8. Computably enumerable set - Wikipedia

    en.wikipedia.org/wiki/Computably_enumerable_set

    A recursively enumerable language is a computably enumerable subset of a formal language. The set of all provable sentences in an effectively presented axiomatic system is a computably enumerable set. Matiyasevich's theorem states that every computably enumerable set is a Diophantine set (the converse is trivially true).

  9. Knuth's Algorithm X - Wikipedia

    en.wikipedia.org/wiki/Knuth's_Algorithm_X

    In other words, the subcollection {B, D, F} is an exact cover, since every element is contained in exactly one of the sets B = {1, 4}, D = {3, 5, 6}, or F = {2, 7}.There are no more selected rows at level 3, thus the algorithm moves to the next branch at level 2…