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Hometriskaidekaphobia

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# triskaidekaphobia

*Triskaidekaphobia* is the irrational fear of the number 13. This fear is recognized as a mental disorder by the Diagnostic and Statistical Manual of Mental Disorders IV (DSM-IV). Few mathematicians suffer from triskaidekaphobia; generally it’s artists who are afflicted. For example, the composer Arnold Schoenberg and the pianist Glenn Gould. However, Benjamin Franklin was mildly afflicted: if there were 13 people at his dinner table, he would call for his secretary to join the party. He was apparently not bothered by the fact that the United States at the time consisted of 13 states and the flag had 13 stars and 13 stripes. The rationale for Franklin’s affliction seems to have been that there were 13 people at the Last Supper of Jesus Christ. Architects for the most part don’t have to worry about triskaidekaphobia when building new buildings, but when working on existing buildings they have to remember to subtract one if the building’s 13th floor was renumbered 14.

# References

- 1 W. Clarke, Some Mathematical History: The History of Numbers (2003): 7

## Mathematics Subject Classification

00A99*no label found*

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## Comments

## 13-phobia: some PM users, too

If my calculations are correct, PM users are afflicted by 13-phobia: there has never been a new addition to the PlanetMath encyclopedia on a Friday the 13th.

Though of course I could have miscalculated, I have miscalculated before. For example, I wanted a canonical object ID# that is a multiple of 13. I was off by 2.

Now to get rid of this object before any bad luck attaches to me.

## Re: 13-phobia: some PM users, too

It certainly is true of the previous Friday the 13th (on the 14th there was a major influx of new entries). But perhaps if we look far back enough we might be able to find one besides your entry today. Perhaps you ought to revise the statement in your entry to specify "professional mathematicians." Amateurs like us appear quite vulnerable to this psychiatric disorder!