OFFSET
1,1
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
KEYWORD
easy,nonn
AUTHOR
Cino Hilliard, Mar 04 2003
STATUS
approved