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A111348
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Numbers n such that the result of swapping the 3rd and next to the next to the last digit of a number is prime.
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2
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101, 104, 106, 107, 110, 112, 113, 118, 119, 124, 125, 128, 130, 131, 133, 134, 136, 140, 142, 145, 146, 149, 151, 152, 157, 160, 164, 166, 167, 170, 172, 175, 179, 181, 182, 188, 191, 194, 196, 199, 200, 300, 301, 305, 310, 311, 313, 316, 320, 322, 325
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OFFSET
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1,1
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COMMENTS
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Similar to A095179 for the first few terms.
Since these numbers are just digit permutations of the primes the sequence is obviously infinite. - Charles R Greathouse IV, Oct 20 2008
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LINKS
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FORMULA
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For N1=a(n)*10^n+a(n-1)*10^(n-1)+a(n-2)*10^(n-2)+...+a(2)*10^2+a(1)*10 + a(0), N2=a(n)*10^n+a(n-1)*10^(n-1)+a(2)*10^(n-2)+...+a(n-2)*10^2+a(1)*10 + a(0) is prime.
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PROG
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(PARI) swapn(n, d) = \ d is the digit position to swap { local(j, ln, x, s, y, y2, tmp); for(x=10^(d-1), 10^(d-1)+n, s = Str(x); ln = length(s); y = eval(Vec(s)); tmp=y[d]; y[d]=y[ln-d+1]; y[ln-d+1]=tmp; y2=0; for(j=1, ln, y2+=y[j]*10^(ln-j); ); if(isprime(y2), print1(x", ")) ) }
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CROSSREFS
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KEYWORD
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easy,nonn,base
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AUTHOR
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STATUS
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approved
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