Number of base-2 strong pseudoprimes (A001262) less than 2^n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =0a(9) =0a(10) =1a(11) =3a(12) =4a(13) =6a(14) =7a(15) =11a(16) =18a(17) =24a(18) =34a(19) =49a(20) =75a(21) =104a(22) =147a(23) =210a(24) =296a(25) =409a(26) =552a(27) =734a(28) =981a(29) =1311