Steinhaus–Moser notation: Difference between revisions
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Steinhaus only defined the triangle, the square, and a '''circle''' [[image:Circle-n.svg|20px|n in a circle]], equivalent to the pentagon defined above. |
Steinhaus only defined the triangle, the square, and a '''circle''' [[image:Circle-n.svg|20px|n in a circle]], equivalent to the pentagon defined above. |
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== Special values == |
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Steinhaus defined: |
Steinhaus defined: |
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*'''mega''' is the number equivalent to 2 in a circle: ② |
*'''mega''' is the number equivalent to 2 in a circle: ② |
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**mega = <math>M(2,1,5)</math> |
**mega = <math>M(2,1,5)</math> |
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**moser = <math>M(2,1,M(2,1,5))</math> |
**moser = <math>M(2,1,M(2,1,5))</math> |
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=== See also === |
=== See also === |
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* [[Ackermann’s function]] |
* [[Ackermann’s function]] |
Revision as of 22:36, 5 October 2008
In mathematics, Steinhaus–Moser notation is a means of expressing certain extremely large numbers. It is an extension of Steinhaus’s polygon notation.
Definitions
- a number n in a triangle means nn.
- a number n in a square is equivalent with "the number n inside n triangles, which are all nested."
- a number n in a pentagon is equivalent with "the number n inside n squares, which are all nested."
etc.: n written in an (m + 1)-sided polygon is equivalent with "the number n inside n nested m-sided polygons. In a series of nested polygons, they are associated inward. The number n inside two triangles is equivalent to nn inside one triangle, which is equivalent to nn raised to the power of nn.
Steinhaus only defined the triangle, the square, and a circle , equivalent to the pentagon defined above.
Special values
Steinhaus defined:
- mega is the number equivalent to 2 in a circle: ②
- megiston is the number equivalent to 10 in a circle: ⑩
Moser’s number is the number represented by "2 in a megagon", where a megagon is a polygon with a "mega" sides.
Alternative notations:
- use the functions square(x) and triangle(x)
- let M(n, m, p) be the number represented by the number n in m nested p-sided polygons; then the rules are:
- and
- mega =
- moser =
See also
Mega
Note that ② is already a very large number, since ② = square(square(2)) = square(triangle(triangle(2))) = square(triangle(22)) = square(triangle(4)) = square(44) = square(256) = triangle(triangle(triangle(...triangle(256)...))) [256 triangles] = triangle(triangle(triangle(...triangle(256256)...))) [255 triangles] = triangle(triangle(triangle(...triangle(3.2 × 10616)...))) [255 triangles] = ...
Using the other notation:
mega = M(2,1,5) = M(256,256,3)
With the function we have mega = where the superscript denotes a functional power, not a numerical power.
We have (note the convention that powers are evaluated from right to left):
- M(256,2,3) =
- M(256,3,3) = ≈
Similarly:
- M(256,4,3) ≈
- M(256,5,3) ≈
etc.
Thus:
- mega = , where denotes a functional power of the function .
Rounding more crudely (replacing the 257 at the end by 256), we get mega ≈ , using Knuth's up-arrow notation.
Note that after the first few steps the value of is each time approximately equal to . In fact, it is even approximately equal to (see also approximate arithmetic for very large numbers). Using base 10 powers we get:
- ( is added to the 616)
- ( is added to the , which is negligible; therefore just a 10 is added at the bottom)
...
- mega = , where denotes a functional power of the function . Hence
Moser's number << Graham's number
It has been proven that in Conway chained arrow notation,
- ,
and, in Knuth's up-arrow notation,
Therefore Moser's number, although incomprehensibly large, is practically unnoticeable compared to Graham's number: