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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. Square triangular number - Wikipedia

    en.wikipedia.org/wiki/Square_triangular_number

    In 1778 Leonhard Euler determined the explicit formula [1] [2]: 12 ... and triangle involved. We have [3]: (12) ... form of a triangular number, and as the product of ...

  4. Pentagonal number - Wikipedia

    en.wikipedia.org/wiki/Pentagonal_number

    The nth pentagonal number p n is the number of distinct dots in a pattern of dots consisting of the outlines of regular pentagons with sides up to n dots, when the pentagons are overlaid so that they share one vertex. For instance, the third one is formed from outlines comprising 1, 5 and 10 dots, but the 1, and 3 of the 5, coincide with 3 of ...

  5. Polygonal number - Wikipedia

    en.wikipedia.org/wiki/Polygonal_number

    A computer search for pentagonal square triangular numbers has yielded only the trivial value of 1, though a proof that there are no other such numbers has yet to be found. [ 5 ] The number 1225 is hecatonicositetragonal ( s = 124 ), hexacontagonal ( s = 60 ), icosienneagonal ( s = 29 ), hexagonal, square, and triangular.

  6. Squared triangular number - Wikipedia

    en.wikipedia.org/wiki/Squared_triangular_number

    A square whose side length is a triangular number can be partitioned into squares and half-squares whose areas add to cubes. From Gulley (2010).The n th coloured region shows n squares of dimension n by n (the rectangle is 1 evenly divided square), hence the area of the n th region is n times n × n.

  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. Figurate number - Wikipedia

    en.wikipedia.org/wiki/Figurate_number

    a number represented as a discrete r-dimensional regular geometric pattern of r-dimensional balls such as a polygonal number (for r = 2) or a polyhedral number (for r = 3). a member of the subset of the sets above containing only triangular numbers, pyramidal numbers, and their analogs in other dimensions. [1]

  9. Pyramidal number - Wikipedia

    en.wikipedia.org/wiki/Pyramidal_number

    Geometric representation of the square pyramidal number 1 + 4 + 9 + 16 = 30. A pyramidal number is the number of points in a pyramid with a polygonal base and triangular sides. [1] The term often refers to square pyramidal numbers, which have a square base with four sides, but it can also refer to a pyramid with any number of sides. [2]