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A217386
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Emirps (A006567) whose difference with the reversal is a perfect square.
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4
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37, 73, 1237, 3019, 7321, 9103, 104801, 105601, 106501, 108401, 111211, 112111, 120121, 121021, 137831, 138731, 144541, 145441, 150151, 151051, 161561, 165161, 167861, 168761, 171271, 172171, 180181, 181081, 185681, 186581, 189337, 194891, 198491, 302647, 305603, 306503
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OFFSET
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1,1
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COMMENTS
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The differences are multiples of 36.
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LINKS
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EXAMPLE
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37 and 73 are primes. 73 - 37 = 36, which is 6^2.
302647 is prime, the reversal 746203 is also prime. 746203 - 302547 = 443556 = 666^2.
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PROG
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(PARI) isinteger(n)=(n==truncate(n))
reverse(n)=eval(concat(Vecrev(Str(n))))
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) }
{for(i=2, 10^7, p=reverse(i); if(isprime(i)&&isprime(p)&&isquare(abs(i-p)), print1(i, " ")))} /* Antonio Roldán, Dec 20 2012 */
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CROSSREFS
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KEYWORD
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nonn,base
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AUTHOR
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STATUS
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approved
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