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Infra notation is a notation for large numbers made by Wikia user Nirvana Supermind.[1].

The notation is currently composed of 1 parts, which is as follows:

## Basic notation

### Current version

All information here only applies to the latest version of the notation.

Basic Infra Notation (BIN) is the 1st part of Infra Notation.[3] An array is of the form I<>, I<a>, or I<a,b>. The numbers inside the angle brackets are called entries. All numbers in the array must be positive integers. It’s the simplest and weakest one. The rules for it are

1. I<> = 0
2. I<a> = 10a
3. I<#,1> = I<#>
4. I<a,b> = I<I<...<I<a,b-1>,b-1>,...>,b-1> (b>0) for a times

Where # is a part of said array (a string of entries and commas, it can also be empty). If there are two or more distinct rules to apply to a single expression, the uppermost-numbered rule which is applicable and whose result is a valid expression will be applied. The creator said that this notation most likely reaches $\displaystyle fω(n)$ in the Fast-growing hierarchy.

#### Example

I<3,1>

= I<I<...<I<3,0>,0>,...>,0> for 3 times

= I<I<I<3,0>,0>,0>

= I<I<<I<3>>>

= 10101000

### Old version

An old version of the notation had the input be an array of nonnegative integers instead[2]. It also had the rule "I<#,0> = I<#>" instead of the current third rule. I<0,1> is ill-defined because there is no rule applied to it. The first three rules are not applicable to it. The fourth rule is applicable to it, but the result is not defined, as the description "for 0 times" itself is ambiguous.

However, the creator fixed those issues.

#### Example

I<0,1> = ill-defined

## Sources

1. Nirvana Supermind. Infra Notation - Integral View
2. Nirvana Supermind. Basic Infra Notation - Integral View. Retrieved Wed, 09 Dec 2020 10:34:00 GMT.
3. {{cite web||last=Nirvana Supermind|url=https://integralview.wordpress.com/2020/12/08/basic-infra-notation/%7Ctitle=Basic Infra Notation - Integral View|accessdate=Wed, 09 Dec 2020 23:47:08 GMT}
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