a(0) = 1; a(n) = half of the a(n-1)-th even nontotient number.

Terms

a(0) =1a(1) =7a(2) =34a(3) =115a(4) =298a(5) =677a(6) =1431a(7) =2853a(8) =5401a(9) =9813a(10) =17289a(11) =29687a(12) =49901a(13) =82315a(14) =133617a(15) =213801a(16) =337742a(17) =527231a(18) =814218a(19) =1244962a(20) =1886069a(21) =2833392a(22) =4223121a(23) =6247850a(24) =9179762a(25) =13399951a(26) =19440903a(27) =28043882a(28) =40233399a(29) =57423953