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

1,1

Links

Table of n, a(n) for n=1..30.

Formula

Let prime(i) = i-th prime, let twin(n) = (P, Q) be n-th pair of twin primes; sequence gives prime(P)*Q.

Example

The 3rd pair of twin primes is twin(3) = (11,13), prime(11) = 31, a(3) = 31*13 = 403.

Prog

(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) }

Crossrefs

Cf. A057470.

Sequence in context: A192504 A363635 A033658 * A134153 A251311 A223181

Adjacent sequences: A080696 A080697 A080698 * A080700 A080701 A080702

Keyword

easy,nonn

Author

Cino Hilliard, Mar 04 2003

Status

approved