Number of even nontotients not exceeding 2^n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =2a(5) =6a(6) =17a(7) =41a(8) =94a(9) =215a(10) =470a(11) =1004a(12) =2126a(13) =4449a(14) =9278a(15) =19177a(16) =39388a(17) =80698a(18) =164808a(19) =335809a(20) =683117a(21) =1387415a(22) =2813664a(23) =5700228a(24) =11536241a(25) =23324624a(26) =47122764a(27) =95134678a(28) =191937316a(29) =387024829