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

Terms

a(0) =0a(1) =1a(2) =3a(3) =7a(4) =21a(5) =60a(6) =166a(7) =463a(8) =1281a(9) =3521a(10) =9645a(11) =26322a(12) =71606a(13) =194283a(14) =525897a(15) =1420595a(16) =3830445a(17) =10311510a(18) =27718028a(19) =74410105a(20) =199519155a(21) =534400491a(22) =1429944603a(23) =3822761742a(24) =10211093226a(25) =27254110405a(26) =72691102131a(27) =193750155673a(28) =516100470051