The cache is not at the posted coordinates. However, you can park there, cross over Vollmerhausen Road, and take the trail that starts at N 39° 09.641 W 076° 50.968 to within 50~100 ft of the cache.
To find the cache, you first need to complete the numerical sequence 10, 10, 11, 12, 15, 16, 21, AB, CD, EF.
The cache is located at N39 09.XXX W076 50.YYY where
XXX = 100(A+C) +10(B) +(C+E)
YYY = 100(E+F) + 10(B) +(B+C+D)
Not sure how difficult the puzzle is? Mark (mmammel) said it took him ~10 minutes to solve it but he mentioned that his son solved it in 30 seconds!