Number of series-parallel networks with n unlabeled edges. Also called yoke-chains by Cayley and MacMahon.

A000084

Number of series-parallel networks with n unlabeled edges. Also called yoke-chains by Cayley and MacMahon.

Terms

    a(0) =1a(1) =2a(2) =4a(3) =10a(4) =24a(5) =66a(6) =180a(7) =522a(8) =1532a(9) =4624a(10) =14136a(11) =43930a(12) =137908a(13) =437502a(14) =1399068a(15) =4507352a(16) =14611576a(17) =47633486a(18) =156047204a(19) =513477502a(20) =1696305728a(21) =5623993944a(22) =18706733128a(23) =62408176762a(24) =208769240140a(25) =700129713630

External references