login
This site is supported by donations to The OEIS Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
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

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

License Agreements, Terms of Use, Privacy Policy. .

Last modified October 14 07:19 EDT 2019. Contains 327995 sequences. (Running on oeis4.)