Search results
Results from the WOW.Com Content Network
He does not go further than this, but from this it follows that the sum of the first n cubes equals the sum of the first n(n + 1) / 2 odd numbers, that is, the odd numbers from 1 to n(n + 1) − 1. The average of these numbers is obviously n(n + 1) / 2 , and there are n(n + 1) / 2 of them, so their sum is ( n(n + 1 ...
The n-th harmonic number, which is the sum of the reciprocals of the first n positive integers, is never an integer except for the case n = 1. Moreover, József Kürschák proved in 1918 that the sum of the reciprocals of consecutive natural numbers (whether starting from 1 or not) is never an integer.
This is also equal to the sum of the first n odd numbers as can be seen in the above pictures, where a square results from the previous one by adding an odd number of points (shown in magenta). The formula follows: n 2 = ∑ k = 1 n ( 2 k − 1 ) . {\displaystyle n^{2}=\sum _{k=1}^{n}(2k-1).}
This gnomonic technique also provides a proof that the sum of the first n odd numbers is n 2; the figure illustrates 1 + 3 + 5 + 7 + 9 + 11 + 13 + 15 = 64 = 8 2. First five terms of Nichomachus's theorem. Applying the same technique to a multiplication table gives the Nicomachus theorem, proving that each squared triangular number is a sum of ...
The statement that the sum of all positive odd numbers up to 2n − 1 is a perfect square—more specifically, the perfect square n 2 —can be demonstrated by a proof without words. [3] In one corner of a grid, a single block represents 1, the first square. That can be wrapped on two sides by a strip of three blocks (the next odd number) to ...
Therefore, the theorem states that it is expressible as the sum of two squares. Indeed, 2450 = 7 2 + 49 2. The prime decomposition of the number 3430 is 2 · 5 · 7 3. This time, the exponent of 7 in the decomposition is 3, an odd number. So 3430 cannot be written as the sum of two squares.
The number of ways to represent n as the sum of four squares is eight times the sum of the divisors of n if n is odd and 24 times the sum of the odd divisors of n if n is even (see divisor function), i.e.
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. Hence the n th pronic number and the n th square number (the sum of the first n odd integers) form a superparticular ratio: