Number of compositions of n in which the maximal multiplicity of parts equals 2.

Terms

a(0) =1a(1) =0a(2) =4a(3) =6a(4) =10a(5) =21a(6) =40a(7) =87a(8) =121a(9) =219a(10) =421a(11) =690a(12) =1159a(13) =1782a(14) =3304a(15) =5190a(16) =8212a(17) =12897a(18) =22084a(19) =33255a(20) =53617a(21) =82539a(22) =124849a(23) =206172a(24) =313339a(25) =472056a(26) =714976a(27) =1077996a(28) =1682806a(29) =2502645