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A210498 Prime numbers that become emirps when their least-significant-digit is deleted. 4

%I #20 Jul 26 2022 22:00:33

%S 131,137,139,173,179,311,313,317,373,379,719,733,739,797,971,977,1493,

%T 1499,1571,1579,1993,1997,1999,3119,3371,3373,3593,7013,7019,7331,

%U 7333,7393,7433,7517,7691,7699,9371,9377,9413,9419,9533,9539,9677,9679,9719,9833

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

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

%H Christian N. K. Anderson, <a href="/A210498/b210498.txt">Table of n, a(n) for n = 1..10000</a>

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

%o (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;

%o while(len<100)

%o if(isprime((i=nextprime(i))))

%o if(isemirp(as.bigz(substr(i,1,nchar(as.character(i))-1))))

%o y[(len=len+1)]=i

%Y Cf. A006567, A024770, A000040, A225235

%K nonn,base

%O 1,1

%A _Kevin L. Schwartz_ and _Christian N. K. Anderson_, May 03 2013

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