A083820 - OEIS

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.

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

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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