Number of subsets of {1..n} not containing their mean.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =10a(5) =22a(6) =48a(7) =102a(8) =214a(9) =440a(10) =900a(11) =1830a(12) =3706a(13) =7486a(14) =15092a(15) =30380a(16) =61100a(17) =122780a(18) =246566a(19) =494912a(20) =992984a(21) =1991620a(22) =3993446a(23) =8005388a(24) =16044460a(25) =32150584a(26) =64414460a(27) =129037790a(28) =258462026a(29) =517641086