This site is supported by donations to The OEIS Foundation.

Thanks to everyone who made a donation during our annual appeal!
To see the list of donors, or make a donation, see the OEIS Foundation home page.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A080700 Product of upper bound twin-prime-indexed primes and their lower bound twin prime. 0
 33, 85, 451, 1139, 3683, 7831, 16697, 26057, 56863, 64093, 109189, 130673, 194573, 223661, 239749, 328469, 363997, 468329, 519007, 647191, 815797, 1218871, 1301189, 1520839, 1959481, 2363057, 2648179, 2817839, 3068467, 3257437 (list; graph; refs; listen; history; text; internal format)
 OFFSET 1,1 LINKS FORMULA Let prime(i) = i-th prime, let twin(n) = (P, Q) be n-th pair of twin primes; sequence gives prime(Q)*P. EXAMPLE The 3rd pair of twin primes is twin(3) = (11,13), prime(13) = 41, a(3) = 41*11 = 451. MATHEMATICA Prime[Last[#]]First[#]&/@Select[Partition[Prime[Range[200]], 2, 1], Last[#]- First[#] ==2&]  (* Harvey P. Dale, Apr 23 2011 *) PROG (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) } CROSSREFS Cf. A057470, A057473. Sequence in context: A075039 A039833 A250732 * A292366 A080200 A067705 Adjacent sequences:  A080697 A080698 A080699 * A080701 A080702 A080703 KEYWORD easy,nonn AUTHOR Cino Hilliard, Mar 04 2003 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recent
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified January 20 14:40 EST 2019. Contains 319333 sequences. (Running on oeis4.)