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Search: id:A125590
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| A125590 |
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Largest n-digit base-10 deletable prime. |
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+0
2
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| 7, 97, 997, 9973, 99929, 999907, 9999907, 99999307, 999996671, 9999996073, 99999966307, 999999908773, 9999999710639, 99999999697769, 999999997160639, 9999999996977699
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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A prime p is a base-b deletable prime if when written in base b it has the property that removing some digit leaves either the empty string or another deletable prime. "Digit" means digit in base b.
Deleting a digit cannot leave any leading zeros in the new string. For example, deleting the 2 in 2003 to obtain 003 is not allowed.
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REFERENCES
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C. Caldwell, Truncatable primes, J. Recreational Math., 19:1 (1987) 30-33. [Discusses left truncatable primes, right truncatable primes and deletable primes.]
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LINKS
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C. Cardwell, Deletable primes
Prime Curios, A 300-digit example
Prime Puzzles, Puzzle 138: Deletable Primes [Includes a 500-digit example]
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EXAMPLE
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99929 -> 9929 -> 929 -> 29 -> 2.
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CROSSREFS
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Cf. A080608, A096243, A096246, A125589.
Sequence in context: A007810 A114019 A127892 this_sequence A068694 A003618 A093172
Adjacent sequences: A125587 A125588 A125589 this_sequence A125591 A125592 A125593
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KEYWORD
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nonn,base,more
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AUTHOR
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njas, Jan 07 2007
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EXTENSIONS
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a(6) - a(8) from Michael Kleber, Jan 08 2007
Extended through a(17) by Joshua Zucker (joshua.zucker(AT)stanfordalumni.org)
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