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%I #15 Jan 07 2017 00:52:39
%S 33,85,451,1139,3683,7831,16697,26057,56863,64093,109189,130673,
%T 194573,223661,239749,328469,363997,468329,519007,647191,815797,
%U 1218871,1301189,1520839,1959481,2363057,2648179,2817839,3068467,3257437
%N Product of upper bound twin-prime-indexed primes and their lower bound twin prime.
%F Let prime(i) = i-th prime, let twin(n) = (P, Q) be n-th pair of twin primes; sequence gives prime(Q)*P.
%e The 3rd pair of twin primes is twin(3) = (11,13), prime(13) = 41, a(3) = 41*11 = 451.
%t Prime[Last[#]]First[#]&/@Select[Partition[Prime[Range[200]],2,1], Last[#]- First[#] ==2&] (* _Harvey P. Dale_, Apr 23 2011 *)
%o (PARI) twipxpindex3(n) = {sr=0; pr=1; for(x=1,n, p1=prime(x); p2=prime(x+1); if((p2-p1)==2, pr=p1*prime(prime(x+1)); sr+=1.0/pr; print1(pr" ")); ); print(); print(sr) }
%Y Cf. A057470, A057473.
%K easy,nonn
%O 1,1
%A _Cino Hilliard_, Mar 04 2003
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