A080699 Product of twin-prime-indexed primes and their upper bound twin prime.
25, 77, 403, 1121, 3379, 7697, 16897, 25769, 56341, 63983, 107447, 129709, 192403, 222529, 238999, 328157, 361259, 466933, 515909, 645719, 817009, 1219637, 1299433, 1508917, 1952359, 2359943, 2642597, 2815831, 3060037, 3260713
Offset: 1
Examples
The 3rd pair of twin primes is twin(3) = (11,13), prime(11) = 31, a(3) = 31*13 = 403.
Crossrefs
Cf. A057470.
Programs
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PARI
twipxpindex2(n) = {sr=0; pr=1; for(x=1,n, p1=prime(x); p2=prime(x+1); if((p2-p1)==2, pr=p2*prime(prime(x)); sr+=1.0/pr; print1(pr" ")); ); print(); print(sr) }
Formula
Let prime(i) = i-th prime, let twin(n) = (P, Q) be n-th pair of twin primes; sequence gives prime(P)*Q.