OFFSET
1,3
EXAMPLE
First twin-prime average = 4 (=-1+1*5): a(1) = -1.
Second twin-prime average = 6 (=1+1*5): a(2) = +1.
Third twin-prime average = 12 (=2+2*5): a(3) = +2.
MATHEMATICA
Mod[#, 5]&/@(Mean/@Select[Partition[Prime[Range[1000]], 2, 1], Last[#]- First[#]==2&])/.{4->-1, 3->-2} (* Harvey P. Dale, Dec 18 2013 *)
CROSSREFS
KEYWORD
sign
AUTHOR
Greg Huber, Jul 18 2006
STATUS
approved