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  2. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    The n th term describes the length of the n th run ... At each stage an alternating sequence of 1s and 0s is inserted between the terms of the previous sequence.

  3. Pell number - Wikipedia

    en.wikipedia.org/wiki/Pell_number

    In words, the sequence of Pell numbers starts with 0 and 1, and then each Pell number is the sum of twice the previous Pell number, plus the Pell number before that. The first few terms of the sequence are 0, 1, 2, 5, 12, 29, 70, 169, 408, 985, 2378, 5741, 13860, … (sequence A000129 in the OEIS).

  4. Recurrence relation - Wikipedia

    en.wikipedia.org/wiki/Recurrence_relation

    In mathematics, a recurrence relation is an equation according to which the th term of a sequence of numbers is equal to some combination of the previous terms. Often, only previous terms of the sequence appear in the equation, for a parameter that is independent of ; this number is called the order of the relation.

  5. Integer sequence - Wikipedia

    en.wikipedia.org/wiki/Integer_sequence

    Alternatively, an integer sequence may be defined by a property which members of the sequence possess and other integers do not possess. For example, we can determine whether a given integer is a perfect number, (sequence A000396 in the OEIS), even though we do not have a formula for the nth perfect number.

  6. Formulas for generating Pythagorean triples - Wikipedia

    en.wikipedia.org/wiki/Formulas_for_generating...

    Michael Stifel published the following method in 1544. [3] [4] Consider the sequence of mixed numbers,,,, … with = + +.To calculate a Pythagorean triple, take any term of this sequence and convert it to an improper fraction (for mixed number , the corresponding improper fraction is ).

  7. Selection algorithm - Wikipedia

    en.wikipedia.org/wiki/Selection_algorithm

    A notable exception is the Standard Template Library for C++, which provides a templated nth_element method with a guarantee of expected linear time. [ 3 ] Python 's standard library includes heapq.nsmallest and heapq.nlargest functions for returning the smallest or largest elements from a collection, in sorted order.

  8. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    It concerns sequences of integers in which each term is obtained from the previous term as follows: if a term is even, the next term is one half of it. If a term is odd, the next term is 3 times the previous term plus 1. The conjecture is that these sequences always reach 1, no matter which positive integer is chosen to start the sequence.

  9. Padovan sequence - Wikipedia

    en.wikipedia.org/wiki/Padovan_sequence

    The number of ways of writing n as an ordered sum in which no term is 2 is P(2n − 2). For example, P(6) = 4, and there are 4 ways to write 4 as an ordered sum in which no term is 2: 4 ; 1 + 3 ; 3 + 1 ; 1 + 1 + 1 + 1. The number of ways of writing n as a palindromic ordered sum in which no term is 2 is P(n).