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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

%I #15 Aug 25 2014 12:03:43

%S 2,3,5,7,43,47,67,83,97,263,283,293,347,367,383,397,547,563,587,593,

%T 743,787,797,4243,4283,4297,4363,4397,4547,4567,4583,4597,4783,4787,

%U 4793,6247,6263,6287,6343,6367,6397,6547,6563,6763,6793,8243,8263,8287,8293

%N 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.

%C Primes with prime and composite digits interlaced (starting at the right). - _Zak Seidov_, Apr 20 2014

%o (PARI) iscomp(n) = (n != 0) && (n != 1) && ! isprime(n);

%o 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

%Y Cf. A083821.

%K base,nonn

%O 1,1

%A _Amarnath Murthy_ and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 08 2003

%E Corrected and extended by _Ray Chandler_, May 20 2003

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Last modified October 3 16:29 EDT 2023. Contains 365868 sequences. (Running on oeis4.)