OFFSET
1,1
MATHEMATICA
SemiprimeQ[n_] := Plus @@ FactorInteger[n][[All, 2]] == 2; k = 8; Do[a[n] = 1, {n, k + 1}]; a[n_] := a[n] = a[n - k] + a[n - k - 1]; Union[Select[Array[a, 280], SemiprimeQ]]
Union[Select[LinearRecurrence[{0, 0, 0, 0, 0, 0, 0, 1, 1}, {1, 1, 1, 1, 1, 1, 1, 1, 1}, 300], PrimeOmega[#]==2&]] (* Harvey P. Dale, May 07 2015 *)
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Jonathan Vos Post, Feb 05 2005
EXTENSIONS
Edited and extended by Ray Chandler, Feb 10 2005
STATUS
approved