OFFSET
2,1
MATHEMATICA
b = {}; a = {}; Do[If[PrimeQ[((Prime[n + 2] + Prime[n + 1])/2 + (Prime[n + 1] + Prime[n])/2)/2], AppendTo[a, ((Prime[n + 2] + Prime[n + 1])/2 + (Prime[n + 1] + Prime[n])/2)/2]], {n, 1, 100000}]; Do[If[PrimeQ[(a[[k + 1]] + a[[k]])/2], AppendTo[b, (a[[k + 1]] + a[[k]])/2]], {k, 1, Length[a] - 1}]; RealDigits[N[FromContinuedFraction[b], 100]][[1]]
CROSSREFS
KEYWORD
cons,nonn
AUTHOR
Artur Jasinski, Jan 18 2007
EXTENSIONS
Offset corrected by R. J. Mathar, Feb 05 2009
STATUS
approved