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A020994
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Primes that are both left-truncatable and right-truncatable.
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18
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2, 3, 5, 7, 23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397
(list;
graph;
refs;
listen;
history;
text;
internal format)
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OFFSET
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1,1
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COMMENTS
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Two-sided primes: deleting any number of digits at left or at right, but not both, leaves a prime.
Primes in which every digit string containing the most significant digit or the least significant digit is prime. - Amarnath Murthy, Sep 24 2003
Intersection of A024785 and A024770. - Robert Israel, Mar 23 2015
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REFERENCES
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David Wells, The Penguin Dictionary of Curious and Interesting Numbers, p. 178 (Rev. ed. 1997).
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LINKS
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Table of n, a(n) for n=1..15.
I. O. Angell, and H. J. Godwin, On Truncatable Primes Math. Comput. 31, 265-267, 1977.
P. De Geest, The list of 4260 left-truncatable primes
Index entries for sequences related to truncatable primes
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MATHEMATICA
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tspQ[n_] := Module[{idn=IntegerDigits[n], l}, l=Length[idn]; Union[PrimeQ/@(FromDigits/@ Join[Table[Take[idn, i], {i, l}], Table[Take[idn, -i], {i, l}]])]=={True}] Select[Prime[Range[PrimePi[740000]]], tspQ]
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CROSSREFS
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Cf. A033664, A024785, A032437, A024770, A052023, A052024, A052025, A050986, A050987, A254751, A254753.
Sequence in context: A211681 A124674 A177061 * A085823 A284060 A211682
Adjacent sequences: A020991 A020992 A020993 * A020995 A020996 A020997
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KEYWORD
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nonn,fini,full,base
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AUTHOR
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Mario Velucchi (mathchess(AT)velucchi.it)
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EXTENSIONS
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Corrected by David W. Wilson
Additional comments from Harvey P. Dale, Jul 10 2002
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STATUS
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approved
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