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A080699 Product of twin-prime-indexed primes and their upper bound twin prime. 0
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 (list; graph; refs; listen; history; text; internal format)
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: A221309 A192504 A033658 * A134153 A251311 A223181

Adjacent sequences:  A080696 A080697 A080698 * A080700 A080701 A080702

KEYWORD

easy,nonn

AUTHOR

Cino Hilliard, Mar 04 2003

STATUS

approved

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Last modified June 19 17:25 EDT 2021. Contains 345144 sequences. (Running on oeis4.)