Number of twin prime pairs below 10^n.

Terms

a(0) =2a(1) =8a(2) =35a(3) =205a(4) =1224a(5) =8169a(6) =58980a(7) =440312a(8) =3424506a(9) =27412679a(10) =224376048a(11) =1870585220a(12) =15834664872a(13) =135780321665