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The n th pronic number is the sum of the first n even integers, and as such is twice the n th triangular number [1] [2] and n more than the n th square number, as given by the alternative formula n 2 + n for pronic numbers. The n th pronic number is also the difference between the odd square (2n + 1) 2 and the (n+1) st centered hexagonal number.
A composite number is a positive integer that can be formed by multiplying two smaller positive integers. Equivalently, it is a positive integer that has at least one divisor other than 1 and itself. [1][2] Every positive integer is composite, prime, or the unit 1, so the composite numbers are exactly the numbers that are not prime and not a ...
For example, if = (,) and = (,,,), the Kostka number counts the number of ways to fill a left-aligned collection of boxes with 3 in the first row and 2 in the second row with 1 copy of the number 1, 1 copy of the number 2, 2 copies of the number 3 and 1 copy of the number 4 such that the entries increase along columns and do not decrease along ...
In mathematics, and more particularly in number theory, primorial, denoted by "#", is a function from natural numbers to natural numbers similar to the factorial function, but rather than successively multiplying positive integers, the function only multiplies prime numbers. The name "primorial", coined by Harvey Dubner, draws an analogy to ...
Ulam spiral of size 201×201. Black dots represent prime numbers. Diagonal, vertical, and horizontal lines with a high density of prime numbers are clearly visible. For comparison, a spiral with random odd numbers colored black (at the same density of primes in a 200x200 spiral). The Ulam spiral or prime spiral is a graphical depiction of the ...
30,561 10 3,G81 20 ÷ ÷ ÷ 61 10 31 20 = = = 501 10 151 20 30,561 10 ÷ 61 10 = 501 10 3,G81 20 ÷ 31 20 = 151 20 ÷ = (black) The divisor goes into the first two digits of the dividend one time, for a one in the quotient. (red) fits into the next two digits once (if rotated), so the next digit in the quotient is a rotated one (that is, a five). (blue) The last two digits are matched once for ...
By convention, 1 is the first polygonal number for any number of sides. The rule for enlarging the polygon to the next size is to extend two adjacent arms by one point and to then add the required extra sides between those points. In the following diagrams, each extra layer is shown as in red.
3. Subfactorial: if n is a positive integer, !n is the number of derangements of a set of n elements, and is read as "the subfactorial of n". * Many different uses in mathematics; see Asterisk § Mathematics. | 1. Divisibility: if m and n are two integers, means that m divides n evenly. 2.