Steinhaus–Moser notation

In mathematics, Moser's polygon notation is a means of expressing certain extremely large numbers. It is an extension of Steinhaus's polygon notation.

(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 m-sided polygons, which are all nested."

Steinhaus only defined the triangle, the square, and a circle , equivalent to the pentagon defined above.

Steinhaus defined:

• "mega" is the number equivalent to 2 in a circle:
• "megiston" is the number equivalent to 10 in a circle:

Moser's number is the number represented by "2 in a megagon", where a "megagon" is a polygon with "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:
  • $M(n,1,3)=n^{n}$
  • $M(n,1,p+1)=M(n,n,p)$
  • $M(n,m+1,p)=M{\big (}M(n,1,p),m,p{\big )}$

and

• • mega = $M(2,1,5)$
  • moser = $M{\big (}2,1,M(2,1,5){\big )}$

Mega

Note that is already a very large number, since = 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)...))) [254 triangles] = ...

Using the other notation:

mega = M(2,1,5) = M(256,256,3)

With the function $f(x)=x^{x}$ we have mega = $f^{256}(256)=f^{258}(2)$ 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) = $(256^{\,\!256})^{256^{256}}=256^{256^{257}}$
• M(256,3,3) = $(256^{\,\!256^{257}})^{256^{256^{257}}}=256^{256^{257}\times 256^{256^{257}}}=256^{256^{257+256^{257}}}$≈$256^{\,\!256^{256^{257}}}$

Similarly:

• M(256,4,3) ≈ ${\,\!256^{256^{256^{256^{257}}}}}$
• M(256,5,3) ≈ ${\,\!256^{256^{256^{256^{256^{257}}}}}}$

etc.

Thus:

• mega = $M(256,256,3)\approx (256\uparrow )^{256}257$, where $(256\uparrow )^{256}$ denotes a functional power of the function $f(n)=256^{n}$.

Rounding more crudely (replacing the 257 at the end by 256), we get mega ≈ $256\uparrow \uparrow 257$, using Knuth's up-arrow notation.

Note that after the first few steps the value of $n^{n}$ is each time approximately equal to $256^{n}$. In fact, it is even approximately equal to $10^{n}$ (see also approximate arithmetic for very large numbers). Using base 10 powers we get:

• $M(256,1,3)\approx 3.23\times 10^{616}$
• $M(256,2,3)\approx 10^{\,\!1.99\times 10^{619}}$ ($\log _{10}616$ is added to the 616)
• $M(256,3,3)\approx 10^{\,\!10^{1.99\times 10^{619}}}$ ($619$ is added to the $1.99\times 10^{619}$, which is negligible; therefore just a 10 is added at the bottom)

• $M(256,4,3)\approx 10^{\,\!10^{10^{1.99\times 10^{619}}}}$

...

• mega = $M(256,256,3)\approx (10\uparrow )^{255}1.99\times 10^{619}$, where $(10\uparrow )^{255}$ denotes a functional power of the function $f(n)=10^{n}$. Hence $10\uparrow \uparrow 257<{\mbox{mega}}<10\uparrow \uparrow 258$

Moser's number

It has been proven that Moser's number, although extremely large, is smaller than Graham's number.

Therefore, using the Conway chained arrow notation,

${\mbox{moser}}<3\rightarrow 3\rightarrow 65\rightarrow 2$

See also

• Conway chained arrow
• Knuth's up-arrow notation

External links

• Factoid on Big Numbers
• Robert Munafo's Big Numbers, which hints Steinhaus and Moser came up with this notation jointly in the '70s.
• Megistron at mathworld.wolfram.com
• Circle notation at mathworld.wolfram.com