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  2. Polite number - Wikipedia

    en.wikipedia.org/wiki/Polite_number

    A Young diagram representing visually a polite expansion 15 = 4 + 5 + 6. In number theory, a polite number is a positive integer that can be written as the sum of two or more consecutive positive integers. A positive integer which is not polite is called impolite.

  3. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    0, 1, 3, 6, 2, 7, 13, 20, 12, 21, 11, 22, 10, 23, 9, 24, 8, 25, 43, 62, ... "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.

  4. Composition (combinatorics) - Wikipedia

    en.wikipedia.org/wiki/Composition_(combinatorics)

    Each positive integer n has 2 n−1 distinct compositions. Bijection between 3 bit binary numbers and compositions of 4 A weak composition of an integer n is similar to a composition of n , but allowing terms of the sequence to be zero: it is a way of writing n as the sum of a sequence of non-negative integers .

  5. Partition function (number theory) - Wikipedia

    en.wikipedia.org/wiki/Partition_function_(number...

    For a positive integer n, p(n) is the number of distinct ways of representing n as a sum of positive integers. For the purposes of this definition, the order of the terms in the sum is irrelevant: two sums with the same terms in a different order are not considered to be distinct.

  6. Pythagorean triple - Wikipedia

    en.wikipedia.org/wiki/Pythagorean_triple

    Since the sum F(k,m) of k consecutive squares beginning ... There can also exist n − 1 positive integers whose n th powers sum to an ... (7, 15, 20) with area 42 (6 ...

  7. Integer partition - Wikipedia

    en.wikipedia.org/wiki/Integer_partition

    3 + 1 2 + 2 2 + 1 + 1 1 + 1 + 1 + 1. The only partition of zero is the empty sum, having no parts. The order-dependent composition 1 + 3 is the same partition as 3 + 1, and the two distinct compositions 1 + 2 + 1 and 1 + 1 + 2 represent the same partition as 2 + 1 + 1. An individual summand in a partition is called a part.

  8. Legendre's three-square theorem - Wikipedia

    en.wikipedia.org/wiki/Legendre's_three-square...

    Pierre de Fermat gave a criterion for numbers of the form 8a + 1 and 8a + 3 to be sums of a square plus twice another square, but did not provide a proof. [1] N. Beguelin noticed in 1774 [2] that every positive integer which is neither of the form 8n + 7, nor of the form 4n, is the sum of three squares, but did not provide a satisfactory

  9. Perfect number - Wikipedia

    en.wikipedia.org/wiki/Perfect_number

    In number theory, a perfect number is a positive integer that is equal to the sum of its positive proper divisors, that is, divisors excluding the number itself. [1] For instance, 6 has proper divisors 1, 2 and 3, and 1 + 2 + 3 = 6, so 6 is a perfect number. The next perfect number is 28, since 1 + 2 + 4 + 7 + 14 = 28.