login
The OEIS Foundation is supported by donations from users of the OEIS and by a grant from the Simons Foundation.

 

Logo


Hints
(Greetings from The On-Line Encyclopedia of Integer Sequences!)
A069686 Primes whose internal digits form a prime. 12
127, 131, 137, 139, 151, 157, 173, 179, 223, 227, 229, 233, 239, 251, 257, 271, 277, 331, 337, 353, 359, 373, 379, 421, 431, 433, 439, 457, 479, 521, 523, 557, 571, 577, 631, 653, 659, 673, 677, 727, 733, 739, 751, 757, 773, 821, 823, 827, 829, 839, 853 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,1

COMMENTS

Primes that remain prime upon deleting the first and last digits.

LINKS

Christian N. K. Anderson, Table of n, a(n) for n = 1..10000

MATHEMATICA

Select[Range[100, 853], PrimeQ[#] && PrimeQ[FromDigits[Rest[Most[IntegerDigits[#]]]]] &] (* T. D. Noe, Apr 05 2013 *)

PROG

(PARI) {indigs(n)=local(j, a, d); n=n\10; j=1; a=0; while(n>10, d=divrem(n, 10); n=d[1]; a=a+j*d[2]; j=10*j); a} forprime(p=1, 855, if(isprime(indigs(p)), print1(p, ", "))) - Klaus Brockhaus, Nov 06 2002

(R) j=101; y=c(); library(gmp)

while(length(y)<10000) {

x=as.numeric(strsplit(as.character(j), spl="")[[1]])

if(isprime(paste(x[3:length(x)-1], collapse=""))>0) y=c(y, as.numeric(j))

j=nextprime(j)

} # (Christian N. K. Anderson, Apr 05 2013)

CROSSREFS

Cf. A077359, A077360.

Sequence in context: A080540 A334105 A077358 * A077360 A102636 A335314

Adjacent sequences:  A069683 A069684 A069685 * A069687 A069688 A069689

KEYWORD

base,nonn

AUTHOR

Amarnath Murthy, Nov 05 2002

EXTENSIONS

Edited and extended by Klaus Brockhaus, Nov 06 2002

Edited by N. J. A. Sloane at the suggestion of Andrew S. Plewe, May 21 2007

Extended by Christian N. K. Anderson, Apr 05 2013

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 August 8 19:29 EDT 2020. Contains 336298 sequences. (Running on oeis4.)