The only base-2 pseudoprime formed entirely from Fermat primes (17*257).
Smaller of the only known base-2 twin pseudoprime. [Gupta]
The smallest base-2 pseudoprime that is a hexadecimal
repunit: R4 = 0x1111. The second is R7, and by
concatenating them, one has the third, R11. [Yosei]
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