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A125590
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Largest n-digit base-10 deletable prime.
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1
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7, 97, 997, 9973, 99929, 999907, 9999907, 99999307, 999996671, 9999996073, 99999966307, 999999908773, 9999999710639, 99999999697769, 999999997160639, 9999999996977699
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,1
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COMMENTS
| 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
| Angell, I. O. and Godwin, H. J. "On Truncatable Primes." Math. Comput. 31, 265-267, 1977.
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
| Index entries for sequences related to truncatable primes
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
| 99929 -> 9929 -> 929 -> 29 -> 2.
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CROSSREFS
| Cf. A080608, A096243, A096246, A125589.
Sequence in context: A114019 A178007 A127892 * A068694 A158579 A003618
Adjacent sequences: A125587 A125588 A125589 * A125591 A125592 A125593
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KEYWORD
| nonn,base,more
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AUTHOR
| N. J. A. Sloane (njas(AT)research.att.com), Jan 07 2007
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EXTENSIONS
| 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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