Number of symmetric primitive Lucas strings of length n.

Terms

a(0) =1a(1) =2a(2) =3a(3) =4a(4) =10a(5) =12a(6) =28a(7) =40a(8) =54a(9) =90a(10) =132a(11) =180a(12) =260a(13) =392a(14) =450a(15) =752a(16) =918a(17) =1404a(18) =1672a(19) =2600a(20) =2898a(21) =4818a(22) =5336a(23) =8424a(24) =9350a(25) =15288a(26) =16254a(27) =26656a(28) =28594a(29) =46530