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.

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

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 * A042666 A042668 A042664

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