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

 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.

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