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 A083820 Primes in which odd positioned digits are prime and even positioned digits are composite. The least significant digit is taken to be the first digit. 1
 2, 3, 5, 7, 43, 47, 67, 83, 97, 263, 283, 293, 347, 367, 383, 397, 547, 563, 587, 593, 743, 787, 797, 4243, 4283, 4297, 4363, 4397, 4547, 4567, 4583, 4597, 4783, 4787, 4793, 6247, 6263, 6287, 6343, 6367, 6397, 6547, 6563, 6763, 6793, 8243, 8263, 8287, 8293 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 COMMENTS Primes with prime and composite digits interlaced (starting at the right). - Zak Seidov, Apr 20 2014 LINKS Table of n, a(n) for n=1..49. PROG (PARI) iscomp(n) = (n != 0) && (n != 1) && ! isprime(n); isok(p) = {if (! isprime(p), return (0)); rd = digits(subst(Polrev(digits(p)), x, 10)); for (i=1, #rd, if (i % 2, if (! isprime(rd[i]), return (0)), if (! iscomp(rd[i]), return (0))); ); return (1); } \\ Michel Marcus, Apr 20 2014 CROSSREFS Cf. A083821. Sequence in context: A048400 A286319 A090716 * A244556 A279954 A120804 Adjacent sequences: A083817 A083818 A083819 * A083821 A083822 A083823 KEYWORD base,nonn AUTHOR Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 08 2003 EXTENSIONS Corrected and extended by Ray Chandler, May 20 2003 STATUS approved

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Last modified June 2 22:56 EDT 2023. Contains 363102 sequences. (Running on oeis4.)