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  2. Permutation pattern - Wikipedia

    en.wikipedia.org/wiki/Permutation_pattern

    For example, the permutation 314265 has two copies of the dashed pattern 2−31−4, given by the entries 3426 and 3425. For a dashed pattern β and any permutation π, we write β(π) for the number of copies of β in π. Thus the number of inversions in π is 2−1(π), while the number of descents is 21(π).

  3. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    A number that has the same number of digits as the number of digits in its prime factorization, including exponents but excluding exponents equal to 1. A046758: Extravagant numbers: 4, 6, 8, 9, 12, 18, 20, 22, 24, 26, 28, 30, 33, 34, 36, 38, ... A number that has fewer digits than the number of digits in its prime factorization (including ...

  4. Wallpaper group - Wikipedia

    en.wikipedia.org/wiki/Wallpaper_group

    Example C has a different wallpaper group, called p4g or 4*2. The fact that A and B have the same wallpaper group means that they have the same symmetries, regardless of the designs' superficial details; whereas C has a different set of symmetries. The number of symmetry groups depends on the number of dimensions in the patterns.

  5. Look-and-say sequence - Wikipedia

    en.wikipedia.org/wiki/Look-and-say_sequence

    This version of the pea pattern eventually forms a cycle with the two "atomic" terms 23322114 and 32232114. Other versions of the pea pattern are also possible; for example, instead of reading the digits as they first appear, one could read them in ascending order instead (sequence A005151 in the OEIS). In this case, the term following 21 would ...

  6. Fibonacci sequence - Wikipedia

    en.wikipedia.org/wiki/Fibonacci_sequence

    Knowledge of the Fibonacci sequence was expressed as early as Pingala (c. 450 BC–200 BC). Singh cites Pingala's cryptic formula misrau cha ("the two are mixed") and scholars who interpret it in context as saying that the number of patterns for m beats (F m+1) is obtained by adding one [S] to the F m cases and one [L] to the F m−1 cases. [12]

  7. Magic number (programming) - Wikipedia

    en.wikipedia.org/wiki/Magic_number_(programming)

    The term magic number or magic constant refers to the anti-pattern of using numbers directly in source code. This has been referred to as breaking one of the oldest rules of programming, dating back to the COBOL , FORTRAN and PL/1 manuals of the 1960s. [ 1 ]

  8. C-number - Wikipedia

    en.wikipedia.org/wiki/C-number

    The term c-number (classical number) is an old nomenclature introduced by Paul Dirac which refers to real and complex numbers. It is used to distinguish from operators ( q-numbers or quantum numbers) in quantum mechanics .

  9. List of numeral systems - Wikipedia

    en.wikipedia.org/wiki/List_of_numeral_systems

    A form of unary notation called Church encoding is used to represent numbers within lambda calculus. Some email spam filters tag messages with a number of asterisks in an e-mail header such as X-Spam-Bar or X-SPAM-LEVEL. The larger the number, the more likely the email is considered spam. 10: Bijective base-10: To avoid zero: 26: Bijective base-26