Number of Poulet numbers (or pseudoprimes to base 2, A001567) less than 2^n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =0a(8) =1a(9) =3a(10) =8a(11) =13a(12) =19a(13) =32a(14) =45a(15) =64a(16) =89a(17) =124a(18) =175a(19) =251a(20) =361a(21) =502a(22) =693a(23) =944a(24) =1264a(25) =1713a(26) =2361a(27) =3169a(28) =4232a(29) =5749