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# Iban Number

By way of analogy with the eban numbers, iban numbers are defined as numbers whose English names do not contain the letter "i" (i.e., "i" is banned). The first few are 1, 2, 3, 4, 7, 10, 11, 12, 14, 17, 20, 21, 22, 23, 24, 27, 40, ... (OEIS A089589). Note that this definition is imprecise insofar as special names are sometimes assigned to a few large numbers that do not follow the usual rules for the naming of such numbers.

Ignoring "special" number names such as googol and googolplex, the number name for every power of 10 greater than 5 contains the suffix "-illion," so there are a finite number of iban numbers. In fact, there are a total of 30275 of them, the largest of which is 777777.

A plot of the first few iban numbers represented as a sequence of binary bits is shown above. The top portion shows the first 255 values, and the bottom shows the next 510 values.

Aban Number, Eban Number, Number, Oban Number, Uban Number

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## References

Sloane, N. J. A. Sequence A089589 in "The On-Line Encyclopedia of Integer Sequences."

Iban Number

## Cite this as:

Weisstein, Eric W. "Iban Number." From MathWorld--A Wolfram Web Resource. https://mathworld.wolfram.com/IbanNumber.html