A210498 Prime numbers that become emirps when their least-significant-digit is deleted.

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

Cf. A006567, A024770, A000040, A225235

Sequence in context: A291620 A356374 A145096 * A050671 A095317 A357075

Adjacent sequences: A210495 A210496 A210497 * A210499 A210500 A210501

Keyword

nonn,base

Author

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

Status

approved