Number of weakly alternating compositions of n.

Terms

a(0) =1a(1) =1a(2) =2a(3) =4a(4) =8a(5) =16a(6) =28a(7) =52a(8) =91a(9) =161a(10) =280a(11) =491a(12) =850a(13) =1483a(14) =2573a(15) =4469a(16) =7757a(17) =13472a(18) =23378a(19) =40586a(20) =70438a(21) =122267a(22) =212210a(23) =368336a(24) =639296a(25) =1109620a(26) =1925916a(27) =3342755a(28) =5801880a(29) =10070133