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PROG
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(PARI) for(n=1, 5, pdn=vector(10^n-10^(n-1)); i=1; for(k=10^(n-1)+1, 10^n-3, if(isprime(k), pdn[i]=k; i++)); s=0; for(l=1, i-1, for(m=1, i-1, if(isprime(pdn[l]*(10^n)+pdn[m]), s++))); print1(s", ")) - Herman Jamke (hermanjamke(AT)fastmail.fm), Mar 30 2008
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