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A083821 Primes in which odd positioned digits are composite and even positioned digits are primes. The least significant digit is the taken to be the first digit. 1
29, 59, 79, 439, 479, 659, 829, 839, 859, 929, 2459, 2659, 2879, 2939, 3659, 3929, 5479, 5639, 5659, 5839, 5879, 5939, 7459, 7639, 7829, 7879, 42829, 42839, 42859, 42929, 42979, 45439, 45659, 45959, 45979, 47459, 47629, 47639, 47659, 47939 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Terms are == 9 (mod 10).

LINKS

Table of n, a(n) for n=1..40.

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 (! iscomp(rd[i]), return (0)), if (! isprime(rd[i]), return (0))); ); return (1); } \\ Michel Marcus, Apr 20 2014

CROSSREFS

Cf. A083820.

Sequence in context: A080170 A078848 A055784 * A055785 A042666 A042668

Adjacent sequences:  A083818 A083819 A083820 * A083822 A083823 A083824

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy and Meenakshi Srikanth (menakan_s(AT)yahoo.com), May 08 2003

EXTENSIONS

More terms from Ray Chandler, May 20 2003

STATUS

approved

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Last modified May 11 16:11 EDT 2021. Contains 343795 sequences. (Running on oeis4.)