Number of lattice n-gons with ordered sides 1, 2, 3, ..., n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =0a(4) =0a(5) =0a(6) =0a(7) =3a(8) =0a(9) =0a(10) =5a(11) =6a(12) =0a(13) =0a(14) =584a(15) =882a(16) =0a(17) =0a(18) =18026a(19) =194741a(20) =0a(21) =0a(22) =644414a(23) =960834a(24) =0a(25) =0a(26) =229910636