Number of ways to fold a strip of n blank stamps.

Terms

a(0) =1a(1) =1a(2) =2a(3) =5a(4) =14a(5) =38a(6) =120a(7) =353a(8) =1148a(9) =3527a(10) =11622a(11) =36627a(12) =121622a(13) =389560a(14) =1301140a(15) =4215748a(16) =14146335a(17) =46235800a(18) =155741571a(19) =512559195a(20) =1732007938a(21) =5732533570a(22) =19423092113a(23) =64590165281a(24) =219349187968a(25) =732358098471