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 A211682 Prime numbers such that all the substrings of length <= 2 are primes. 54
 2, 3, 5, 7, 23, 37, 53, 73, 373, 237373, 537373, 5373737, 53737373, 53737373737, 237373737373, 737373737373737, 53737373737373737, 373737373737373737373, 53737373737373737373737, 53737373737373737373737373, 373737373737373737373737373, 5373737373737373737373737373737 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS A211681 restricted to primes. Contains A085823. In contrast to A085823 this sequence seems to be not finite (conjecture). LINKS Giovanni Resta, Table of n, a(n) for n = 1..36 (terms < 10^1000) EXAMPLE a(10)=237373, since all substrings of length <= 2 are primes (2, 3, 7, 23, 37, 73) and 237373 is prime. CROSSREFS Cf. A085823, A019546, A046034, A211681. Sequence in context: A020994 A085823 A284060 * A100552 A210566 A155873 Adjacent sequences: A211679 A211680 A211681 * A211683 A211684 A211685 KEYWORD nonn,base AUTHOR Hieronymus Fischer, Apr 30 2012 EXTENSIONS The originally submitted terms with index 20 and 21 are composite and have been erased therefore. - Hieronymus Fischer, Sep 24 2018 a(20)-a(22) from Giovanni Resta, Oct 08 2018 STATUS approved

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Last modified April 21 13:26 EDT 2024. Contains 371870 sequences. (Running on oeis4.)