(n-1)-st elementary symmetric function of the first n terms of (1,2,1,2,1,2,1,2,1,2,...)=A000034.

Terms

a(0) =1a(1) =3a(2) =5a(3) =12a(4) =16a(5) =36a(6) =44a(7) =96a(8) =112a(9) =240a(10) =272a(11) =576a(12) =640a(13) =1344a(14) =1472a(15) =3072a(16) =3328a(17) =6912a(18) =7424a(19) =15360a(20) =16384a(21) =33792a(22) =35840a(23) =73728a(24) =77824a(25) =159744a(26) =167936a(27) =344064a(28) =360448a(29) =737280