Numerator of sum_{k=1..n} 1/2^prime(k).

Terms

a(0) =1a(1) =3a(2) =13a(3) =53a(4) =849a(5) =3397a(6) =54353a(7) =217413a(8) =3478609a(9) =222630977a(10) =890523909a(11) =56993530177a(12) =911896482833