Number of (1,0)-steps at level 0 in all weighted lattice paths in L_n.

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =19a(5) =50a(6) =130a(7) =341a(8) =893a(9) =2337a(10) =6119a(11) =16020a(12) =41940a(13) =109801a(14) =287463a(15) =752587a(16) =1970299a(17) =5158310a(18) =13504630a(19) =35355581a(20) =92562113a(21) =242330757a(22) =634430159a(23) =1660959720a(24) =4348449000a(25) =11384387281a(26) =29804712843a(27) =78029751247a(28) =204284540899