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A225235
Emirps whose internal digits are also an emirp.
4
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
KEYWORD
nonn,base,less
STATUS
approved