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 A020994 Primes that are both left-truncatable and right-truncatable. 14
 2, 3, 5, 7, 23, 37, 53, 73, 313, 317, 373, 797, 3137, 3797, 739397 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS 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 REFERENCES David Wells, The Penguin Dictionary of Curious and Interesting Numbers, p. 178 (Rev. ed. 1997). LINKS 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 MATHEMATICA 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] CROSSREFS Cf. A033664, A024785, A032437, A024770, A052023, A052024, A052025, A050986, A050987, A254751, A254753. Sequence in context: A211681 A124674 A177061 * A085823 A211682 A100552 Adjacent sequences:  A020991 A020992 A020993 * A020995 A020996 A020997 KEYWORD nonn,fini,full,base AUTHOR Mario Velucchi (mathchess(AT)velucchi.it) EXTENSIONS Corrected by David W. Wilson Additional comments from Harvey P. Dale, Jul 10 2002 STATUS approved

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