Lengths of the B blocks associated with A091787.

Terms

a(0) =1a(1) =4a(2) =13a(3) =42a(4) =127a(5) =382a(6) =1149a(7) =3448a(8) =10345a(9) =31044a(10) =93133a(11) =279400a(12) =838203a(13) =2514610a(14) =7543831a(15) =22631496a(16) =67894489a(17) =203683468a(18) =611050413a(19) =1833151240a(20) =5499453721a(21) =16498361166a(22) =49495083499a(23) =148485250498a(24) =445455751497