Number of compositions of n avoiding equidistant 3-term arithmetic progressions.

Terms

a(0) =1a(1) =1a(2) =2a(3) =3a(4) =7a(5) =13a(6) =22a(7) =41a(8) =74a(9) =133a(10) =233a(11) =400a(12) =714a(13) =1209a(14) =2091a(15) =3591a(16) =6089a(17) =10316a(18) =17477a(19) =29413a(20) =49515a(21) =82474a(22) =137659a(23) =228461a(24) =377936a(25) =623710a(26) =1025445a(27) =1680418a(28) =2746242a(29) =4474654