And I refer to these reciprocal sums associated with (x – 1)n = 0 as
the Alternative Zeta 2 function i.e. Alt ζ2(n).
However it is possible now to provide a more general
formula.
This is based on the fact that the nth term of these unique
number sequences follow a definite pattern.
Then, for (x
– 1)2, the unique number sequence is 1, 2, 3, 4 with the kth = k and the
∞ ∞
sum of terms = ∑ k/1! with (infinite) sum of reciprocals =
∑1!/k.
k=1 n=1
For (x –
1)3, the unique number sequence is 1, 3, 6, 10, … with
the kth term = k(k + 1)/2!
∞ ∞
And sum of terms = ∑k(k
+ 1)/2! with sum of reciprocals = ∑ 2!/{k(k + 1)}.
k=1 k=1
Then,
giving one more example to illustrate a consistent pattern, for (x –
1)4, the unique number sequence is 1, 4, 10, 20, …, with kth
term = k(k + 1)(k + 2)/3!
∞
So
the (infinite) sum of reciprocals = ∑ 3!/{k(k + 1)(k + 2)}.
k=1
Therefore for the general case (x – 1)n = 0, the (infinite)
sum of reciprocals of the associated unique number sequences of this simple
polynomial equation i.e. Alt ζ2(n), is given as
∞
∑ (k – 1)!/{k(k + 1)(k + 2) … (k + n – 2)}.
k=1
Note, however that the Alt ζ2(n) function remains
undefined for n = 1!
A fascinating geometrical way of looking at the unique
number sequences given by
(x –
1)n = 0, is through number patterns that are associated with the
simplest perfectly symmetrical objects that can be constructed in the various
dimensions.
For example the simplest symmetrical polygon figure (with
least number of sides) that can be constructed in 2-dimensional space is a
3-sided equilateral triangle.
So we start with 1 dot and with the construction of an
equilateral triangle we then place a dot at each vertex = 3. Then by placing a
dot midway along each line, the total no. of points = 6.
And then with 4 dots equally spaced out along each line (with another placed
within the triangle), when the total no. = 10 (overall) we can preserve the perfect symmetry of
equal distance between adjacent dots.
Then in the final example we place 5 dots equally spaced on each side of the triangle with 3 more internally = 15 (overall).
What is also interesting here is that we
can join up the dots in each triangle to form a number of smaller triangles that
represents the previous number in the series.
Thus in the simplest case in the 3 dot case we can join the
points to form 1 triangle (which represents the previous number in the
sequence). Then in the case of the 6 dot triangle we can join the dots to form
3 upright triangles (with same orientation to the 1 larger triangle contained).
Then in the case of the 10 dot triangle we can form 6 upright triangles and in the 15 dot triangle 10 upright triangles of same
orientation to larger triangle and so on.
Then the simplest 3-dimensional figure that is perfectly
symmetrical with respect to its angular rotations is the tetrahedron which has
the equilateral triangle as its base.
Though harder to represent (in 2-dimensional) terms, it is
easy enough to see how the number of symmetrically arranged points (associated
with this 4-sided figure follow the unique number sequence associated with (x – 1)4 = 0, i.e.
1, 4, 10, 20, …
So once again we start with 1 dot represented by the red dot
at the top of the diagram (from Mathworld). Then
to picture the simplest symmetrical tetrahedral figure we combine the 3 blue dots (representing the base of a
tetrahedron with the red dot above) to obtain 4.
Then at the next level where each line of the base of the
tetrahedron is divided in 2 we have now 6 green dots which combine the 3 blue
and 1 red above to complete the new tetrahedron with 10 dots. Then with the
next larger tetrahedron, we have 10 brown points at the base combined with the
6, 3 and 1 respectively above to complete the tetrahedron with 20 points.
So we can easily see here how this sequence of dots,
representing the fully symmetrical nature of the 3-dimensional tetrahedron
(with the least number of sides i.e. 4, possible in 3-dimensional space) is the
unique digit sequence for (x –
1)4 = 0, i.e. 1, 4, 10, 20, 35, …
However what is perhaps remarkable is that these insights
can then be extended for the simplest fully symmetrical objects in n-dimensional
space.
Thus - though impossible to properly visualise in 3 or less
dimensions - we can equally envisage for example a 4-dimensional polytope, as a
5-sided equivalent in 4 space dimensions to the 4-sided tetrahedron in 3 space. This is known as a 5-cell or tetrahedral pyramid. (See Wikipedia entry).
Thus once again this contains the least number of sides i.e.
5, that a fully symmetrical object can possess in 4 space dimensions.
So what we can now say therefore is that the unique number
sequence associated with
(x –
1)5 = 0, i.e. 1, 5, 15, 35, 70, …
now describes the appropriate number of equally spaced points with
respect to this object (as the number of points on each side progressively
increases).
Thus in general terms, the unique sequence of numbers
associated with the polynomial equation
(x – 1)n = 0, encodes the manner, in which the equally spaced points of the simplex n-sided fully symmetrical geometrical objects, occurs in (n – 1) space dimensions.
(x – 1)n = 0, encodes the manner, in which the equally spaced points of the simplex n-sided fully symmetrical geometrical objects, occurs in (n – 1) space dimensions.