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%I #5 Oct 01 2013 17:57:47
%S 3,11,59,71,107,179,191,227,239,311,347,419,431,599,659,827,1019,1031,
%T 1091,1319,1427,1487,1607,1619,1787,1871,1931,2027,2087,2111,2267,
%U 2339,2591,2687,2711,2999,3119,3167,3299,3359,3371,3467,3527,3539,3671,3767
%N Lower member p of a pair of twin primes such that p-1 is squarefree.
%H Harvey P. Dale, <a href="/A089188/b089188.txt">Table of n, a(n) for n = 0..1000</a>
%e 71 is included because 71-1 = 2*5*7. 17 is omitted because 17-1 = 2^4.
%t Select[Transpose[Select[Partition[Prime[Range[600]],2,1],#[[2]]-#[[1]]==2&]][[1]],SquareFreeQ[#-1]&] (* _Harvey P. Dale_, Aug 10 2013 *)
%o (PARI) pm1th(n) = { c=0; pc=0; forprime(x=2,n, pc++; y=x-1; if(isprime(x+2), if(issquarefree(y), c++; print1(x","); ) ) ); print(); print(c","pc","c/pc+.0) }
%K easy,nonn
%O 0,1
%A _Cino Hilliard_, Dec 07 2003
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