a(n) = prime(2^n) - 2*n.

Terms

a(0) =1a(1) =3a(2) =13a(3) =45a(4) =121a(5) =299a(6) =705a(7) =1603a(8) =3653a(9) =8141a(10) =17841a(11) =38849a(12) =83991a(13) =180475a(14) =386063a(15) =821609a(16) =1742503a(17) =3681095a(18) =7754039a(19) =16290007a(20) =34135987a(21) =71378525a(22) =148948093a(23) =310248193a(24) =645155147a(25) =1339484145a(26) =2777105075a(27) =5750078991a(28) =11891268343a(29) =24563311249