A225235 Emirps whose internal digits are also an emirp.

1979, 3319, 3371, 3373, 3719, 3733, 7177, 7717, 9133, 9173, 9791, 10177, 10711, 10739, 11071, 11497, 11579, 11677, 13477, 13591, 13597, 17011, 17393, 17519, 19531, 19913, 30139, 30319, 30971, 31139, 31799, 31991, 37619, 39371, 39419, 39839, 70313, 70373, 70717

Offset

1,1

Comments

This sequence (like the emirps) experiences large gaps when the most-significant-digit is {2,4,5,6,8}.

Links

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

Example

7177 and 10177 are in the sequence because both are emirps, and both become the emirp 17 upon deletion of their first and last digits.

Prog

(R) library(gmp); isemirp<-function(x) isprime(x) & (j=paste(rev(unlist(strsplit(as.character(x), split=""))), collapse=""))!=x & isprime(j);
no0<-function(s){ while(substr(s, 1, 1)=="0" & nchar(s)>1) s=substr(s, 2, nchar(s)); s};
i=as.bigz(0); y=as.bigz(rep(0, 100)); len=0;
while(len<100) if(isemirp((i=nextprime(i)))) if(isemirp(as.bigz(no0(substr(i, 2, nchar(as.character(i))-1))))) y[(len=len+1)]=i;
as.vector(y)

Crossrefs

Cf. A210498, A006567, A069686, A210498.

Sequence in context: A108510 A343971 A343972 * A289907 A125490 A237334

Adjacent sequences: A225232 A225233 A225234 * A225236 A225237 A225238

Keyword

nonn,base,less

Author

Kevin L. Schwartz and Christian N. K. Anderson, May 03 2013

Status

approved