triadic prime
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GIMPS has discovered a new largest known prime number: 282589933-1 (24,862,048 digits)

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

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

See Also: Palindrome, Tetradic, Strobogrammatic


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

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