Linear recursion relative of Shallit sequence S(2,6).

Terms

a(0) =2a(1) =6a(2) =19a(3) =61a(4) =196a(5) =630a(6) =2026a(7) =6516a(8) =20957a(9) =67403a(10) =216786a(11) =697242a(12) =2242518a(13) =7212542a(14) =23197479a(15) =74609345a(16) =239963764a(17) =771788146a(18) =2482278710a(19) =7983677420a(20) =25677658553a(21) =82586271223a(22) =265619709074a(23) =854304581182