Sum of binomial(n,k) over cubefree k.

Terms

a(0) =1a(1) =3a(2) =7a(3) =15a(4) =31a(5) =63a(6) =127a(7) =254a(8) =502a(9) =978a(10) =1882a(11) =3600a(12) =6904a(13) =13380a(14) =26332a(15) =52664a(16) =106744a(17) =218232a(18) =447736a(19) =917760a(20) =1873312a(21) =3799920a(22) =7653136a(23) =15306272a(24) =30429856a(25) =60234528a(26) =118956831a(27) =234885092a(28) =464595690a(29) =921868388