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# triadic prime

A**triadic**(or 3-way) prime is one which is invariant upon reflection only along the line they are written on, so the digits may be 0, 1, 3, and 8. (Trigg called these palindromic reflectable in [Trigg83].) A large example of this kind is

10...0111013101110...01where each string of zeros (0...0) is 2509 zeros long!

**See Also:** Palindrome, Tetradic, Strobogrammatic

**References:**

- DO94
H. DubnerandR. Ondrejka, "A PRIMEr on palindromes,"J. Recreational Math.,26:4 (1994) 256--267.- Trigg83
C. W. Trigg, "Reflectable primes,"J. Recreational Math.,15:4 (1982-83) 251-256.

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