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  2. Triangular number - Wikipedia

    en.wikipedia.org/wiki/Triangular_number

    The final digit of a triangular number is 0, 1, 3, 5, 6, or 8, and thus such numbers never end in 2, 4, 7, or 9. A final 3 must be preceded by a 0 or 5; a final 8 must be preceded by a 2 or 7. In base 10, the digital root of a nonzero triangular number is always 1, 3, 6, or 9. Hence, every triangular number is either divisible by three or has a ...

  3. List of types of numbers - Wikipedia

    en.wikipedia.org/wiki/List_of_types_of_numbers

    Such a number is algebraic and can be expressed as the sum of a rational number and the square root of a rational number. Constructible number: A number representing a length that can be constructed using a compass and straightedge. Constructible numbers form a subfield of the field of algebraic numbers, and include the quadratic surds.

  4. Centered triangular number - Wikipedia

    en.wikipedia.org/wiki/Centered_triangular_number

    Each centered triangular number has a remainder of 1 when divided by 3, and the quotient (if positive) is the previous regular triangular number. Each centered triangular number from 10 onwards is the sum of three consecutive regular triangular numbers. For n > 2, the sum of the first n centered triangular numbers is the magic constant for an n ...

  5. Square triangular number - Wikipedia

    en.wikipedia.org/wiki/Square_triangular_number

    All square triangular numbers have the form , where is a convergent to the continued fraction expansion of , the square root of 2. [ 4 ] A. V. Sylwester gave a short proof that there are infinitely many square triangular numbers: If the n {\displaystyle n} th triangular number n ( n + 1 ) 2 {\displaystyle {\tfrac {n(n+1)}{2}}} is square, then ...

  6. Category:Triangles of numbers - Wikipedia

    en.wikipedia.org/wiki/Category:Triangles_of_numbers

    Pages in category "Triangles of numbers" The following 29 pages are in this category, out of 29 total. ... Triangle of partition numbers; Trinomial triangle; W.

  7. Tetrahedral number - Wikipedia

    en.wikipedia.org/wiki/Tetrahedral_number

    Te n is the sum of all products p × q where (p, q) are ordered pairs and p + q = n + 1; Te n is the number of (n + 2)-bit numbers that contain two runs of 1's in their binary expansion. The largest tetrahedral number of the form + + for some integers and is 8436.

  8. List of numbers - Wikipedia, the free encyclopedia

    en.wikipedia.org/wiki/List_of_numbers

    A list of articles about numbers (not about numerals). Topics include powers of ten, notable integers, prime and cardinal numbers, and the myriad system.

  9. List of integer sequences - Wikipedia

    en.wikipedia.org/wiki/List_of_integer_sequences

    A positive integer n for which there is an e > 0 such that ⁠ d(n) / n e ⁠ ≥ ⁠ d(k) / k e ⁠ for all k > 1. A002201: Pronic numbers: 0, 2, 6, 12, 20, 30, 42, 56, 72, 90, ... a(n) = 2t(n) = n(n + 1), with n ≥ 0 where t(n) are the triangular numbers. A002378: Markov numbers: 1, 2, 5, 13, 29, 34, 89, 169, 194, ... Positive integer ...