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Search: id:A020994
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| A020994 |
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Two-sided primes: deleting any number of digits at left or at right, but not both, leaves a prime. |
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+0
10
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| 2, 3, 5, 7, 23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397
(list; graph; listen)
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OFFSET
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1,1
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COMMENT
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Primes in which every digit string containing the most significant digit or the least significant digit is prime. - Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Sep 24 2003
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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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P. De Geest, The list of 4260 left-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.
Sequence in context: A019546 A096148 A124674 this_sequence A085823 A100552 A106711
Adjacent sequences: A020991 A020992 A020993 this_sequence 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 (hpd1(AT)nyu.edu), Jul 10 2002
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