Number of compositions of n that are neither strictly increasing nor strictly decreasing.

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =5a(5) =11a(6) =25a(7) =55a(8) =117a(9) =241a(10) =493a(11) =1001a(12) =2019a(13) =4061a(14) =8149a(15) =16331a(16) =32705a(17) =65461a(18) =130981a(19) =262037a(20) =524161a(21) =1048425a(22) =2096975a(23) =4194097a(24) =8388365a(25) =16776933a(26) =33554103a(27) =67108481a(28) =134217285a(29) =268434945