1-Fibonacci lattice paths.

Terms

a(0) =1a(1) =1a(2) =3a(3) =8a(4) =23a(5) =67a(6) =199a(7) =600a(8) =1834a(9) =5674a(10) =17743a(11) =56011a(12) =178301a(13) =571812a(14) =1845913a(15) =5993985a(16) =19565770a(17) =64168531a(18) =211343740a(19) =698753053a(20) =2318315786a(21) =7716186315a(22) =25757105801a(23) =86208990248a(24) =289253059765a(25) =972729789813