A080700 Product of upper bound twin-prime-indexed primes and their lower bound twin prime.

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

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(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: A039833 A355711 A250732 * A292366 A080200 A067705

Adjacent sequences: A080697 A080698 A080699 * A080701 A080702 A080703

Keyword

easy,nonn

Author

Cino Hilliard, Mar 04 2003

Status

approved