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  2. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    "subtract if possible, otherwise add": a(0) = 0; for n > 0, a(n) = a(n − 1) − n if that number is positive and not already in the sequence, otherwise a(n) = a(n − 1) + n, whether or not that number is already in the sequence.

  3. On-Line Encyclopedia of Integer Sequences - Wikipedia

    en.wikipedia.org/wiki/On-Line_Encyclopedia_of...

    In 2010 an OEIS wiki was created to simplify the ... (here 3, 7, 15, 1, 292, 1, 1, 1 ... For example, if we list the sequence of square numbers as 0, 1, 4, 9, 16, 25 ...

  4. Collatz conjecture - Wikipedia

    en.wikipedia.org/wiki/Collatz_conjecture

    For instance, the first counterexample must be odd because f(2n) = n, smaller than 2n; and it must be 3 mod 4 because f 2 (4n + 1) = 3n + 1, smaller than 4n + 1. For each starting value a which is not a counterexample to the Collatz conjecture, there is a k for which such an inequality holds, so checking the Collatz conjecture for one starting ...

  5. Arithmetic progression - Wikipedia

    en.wikipedia.org/wiki/Arithmetic_progression

    For instance, the sequence 5, 7, 9, 11, 13, 15, . . . is an arithmetic progression with a common difference of 2. If the initial term of an arithmetic progression is a 1 {\displaystyle a_{1}} and the common difference of successive members is d {\displaystyle d} , then the n {\displaystyle n} -th term of the sequence ( a n {\displaystyle a_{n ...

  6. Generating function - Wikipedia

    en.wikipedia.org/wiki/Generating_function

    In mathematics, a generating function is a representation of an infinite sequence of numbers as the coefficients of a formal power series.Generating functions are often expressed in closed form (rather than as a series), by some expression involving operations on the formal series.

  7. Bit-reversal permutation - Wikipedia

    en.wikipedia.org/wiki/Bit-reversal_permutation

    0 8 4 12 2 10 6 14 1 9 5 13 3 11 7 15 Each permutation in this sequence can be generated by concatenating two sequences of numbers: the previous permutation, with its values doubled, and the same sequence with each value increased by one.

  8. 1 + 2 + 3 + 4 + ⋯ - ⋯ - Wikipedia

    en.wikipedia.org/wiki/1_%2B_2_%2B_3_%2B_4_%2B_%E...

    The first six triangular numbers. The partial sums of the series 1 + 2 + 3 + 4 + 5 + 6 + ⋯ are 1, 3, 6, 10, 15, etc.The nth partial sum is given by a simple formula

  9. Simple continued fraction - Wikipedia

    en.wikipedia.org/wiki/Simple_continued_fraction

    This is the (infinite) continued fraction representation of the number. Examples of continued fraction representations of irrational numbers are: √ 19 = [4;2,1,3,1,2,8,2,1,3,1,2,8,...] (sequence A010124 in the OEIS). The pattern repeats indefinitely with a period of 6. e = [2;1,2,1,1,4,1,1,6,1,1,8,...] (sequence A003417 in the OEIS). The ...