OFFSET
1,1
COMMENTS
The sum of the reciprocals converges to 0.4154254016622336549103692152614908366885449298862362851444631680740051...
LINKS
Amiram Eldar, Table of n, a(n) for n = 1..309
EXAMPLE
The first two twin primes are 3 and 5, so the first term is 3 and the second term is 15. The next two twin primes are 5 and 7, so the third term is 5*15=75 and the fourth term is 75*7=525
MATHEMATICA
Rest[FoldList[Times, 1, Flatten[Select[Partition[Prime[Range[30]], 2, 1], Last[#]-First[#]==2&]]]] (* Harvey P. Dale, Mar 16 2011 *)
PROG
(PARI) twprfact(n) = {sr=0; tp = vector(10000); k=1; forprime(j = 3, n, if(nextprime(j+1)-j == 2, tp[k] = j; tp[k+1] = j+2; k+=2; ); ); for(j=1, k-1, y=1; for(i = 1, j, y*=tp[i]; ); print1(y", "); sr+=1.0/y; ); print(); print(sr); }
CROSSREFS
KEYWORD
nonn
AUTHOR
Cino Hilliard, Feb 03 2003
EXTENSIONS
Definition clarified and example provided by Harvey P. Dale, Mar 16 2011
STATUS
approved