A217386 - OEIS

%I #14 Dec 24 2012 02:23:19

%S 37,73,1237,3019,7321,9103,104801,105601,106501,108401,111211,112111,

%T 120121,121021,137831,138731,144541,145441,150151,151051,161561,

%U 165161,167861,168761,171271,172171,180181,181081,185681,186581,189337,194891,198491,302647,305603,306503

%N Emirps (A006567) whose difference with the reversal is a perfect square.

%C The differences are multiples of 36.

%H Antonio Roldán, <a href="/A217386/b217386.txt">Table of n, a(n) for  a(n)<10^6</a>

%e 37 and 73 are primes. 73 - 37 = 36, which is 6^2.

%e 302647 is prime, the reversal 746203 is also prime. 746203 - 302547 = 443556 = 666^2.

%o (PARI) isinteger(n)=(n==truncate(n))

%o reverse(n)=eval(concat(Vecrev(Str(n))))

%o isquare(n)= { local(f,m,p=0); if(n==1,p=1,f=factor(n); m=gcd(f[, 2]); if(isinteger(m/2),p=1));return(p) }

%o {for(i=2,10^7,p=reverse(i);if(isprime(i)&&isprime(p)&&isquare(abs(i-p)),print1(i," ")))} /* Antonio Roldán, Dec 20 2012 */

%Y Subsequence of A006567 and of A158065.

%K nonn,base

%O 1,1

%A _Antonio Roldán_, Oct 02 2012