Number of compositions of n such that the maximal distance between two identical parts equals two.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =1a(5) =4a(6) =6a(7) =13a(8) =23a(9) =42a(10) =68a(11) =119a(12) =197a(13) =324a(14) =530a(15) =823a(16) =1305a(17) =2040a(18) =3162a(19) =4869a(20) =7431a(21) =11076a(22) =16680a(23) =24831a(24) =36785a(25) =54210a(26) =79546a(27) =115967a(28) =167359a(29) =241726