A225235 -id:A225235 - cp's OEIS frontend

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

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

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

			Example: a(1)=131, which becomes 13 upon deletion, which is an emirp.

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

Cf. A006567, A024770, A000040, A225235

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

A214847 Primes that become emirps when their most-significant-digit is deleted.

Original entry on oeis.org

113, 131, 137, 173, 179, 197, 271, 313, 317, 331, 337, 373, 379, 397, 431, 479, 571, 613, 617, 631, 673, 773, 797, 937, 971, 997, 1013, 1031, 1097, 1709, 1733, 1907, 2017, 2113, 2179, 2311, 2347, 2389, 2953, 2971, 3037, 3079, 3167, 3347, 3359, 3389, 3701, 3709

Offset: 1

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

			113 and 1013 are both in the sequence, because upon deletion they become 13, which is an emirp.

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

Cf. A210498, A006567, A024770, A000040, A225235, A225234.

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(as.bigz(no0(substr((i=nextprime(i)),2,200)))))
y[(len=len+1)]=i

A225234 Primes whose internal digits are an emirp.

Original entry on oeis.org

1171, 1319, 1373, 1733, 1973, 1979, 2131, 2137, 2179, 2311, 2371, 2377, 2711, 2713, 2719, 2731, 2791, 2797, 2971, 3137, 3313, 3319, 3371, 3373, 3719, 3733, 3739, 3793, 3797, 4133, 4139, 4177, 4373, 4733, 4793, 4799, 4973, 5171, 5179, 5711, 5717, 5737, 5791

Offset: 1

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

a(414) = 112019 is the first term with an internal even digit.

			Example: 1171 has the emirp 17 as its internal digits.

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

Cf. A210498, A006567, A024770, A000040, A225235, A214847.

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(as.bigz(no0(substr((i=nextprime(i)),2,nchar(as.character(i))-1))))) y[(len=len+1)]=i

cp's OEIS Frontend

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

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A214847 Primes that become emirps when their most-significant-digit is deleted.

Views

Author

Keywords

Examples

Links

Crossrefs

Programs

R

A225234 Primes whose internal digits are an emirp.

Views

Author

Keywords

Comments

Examples

Links

Crossrefs

Programs

R