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A210498
Prime numbers that become emirps when their least-significant-digit is deleted.
4
131, 137, 139, 173, 179, 311, 313, 317, 373, 379, 719, 733, 739, 797, 971, 977, 1493, 1499, 1571, 1579, 1993, 1997, 1999, 3119, 3371, 3373, 3593, 7013, 7019, 7331, 7333, 7393, 7433, 7517, 7691, 7699, 9371, 9377, 9413, 9419, 9533, 9539, 9677, 9679, 9719, 9833
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
Example: a(1)=131, which becomes 13 upon deletion, which is an emirp.
PROG
(R) library(gmp); isemirp<-function(x) isprime(x) & (j=paste(rev(unlist(strsplit(as.character(x), split=""))), collapse=""))!=x & isprime(j); i=as.bigz(0); y=as.bigz(rep(0, 100)); len=0;
while(len<100)
if(isprime((i=nextprime(i))))
if(isemirp(as.bigz(substr(i, 1, nchar(as.character(i))-1))))
y[(len=len+1)]=i
CROSSREFS
KEYWORD
nonn,base
STATUS
approved