Fine's sequence (or Fine numbers): number of relations of valence >= 1 on an n-set; also number of ordered rooted trees with n nodes having root of even degree.
A000957
Fine's sequence (or Fine numbers): number of relations of valence >= 1 on an n-set; also number of ordered rooted trees with n nodes having root of even degree.
Terms
- a(0) =0a(1) =1a(2) =0a(3) =1a(4) =2a(5) =6a(6) =18a(7) =57a(8) =186a(9) =622a(10) =2120a(11) =7338a(12) =25724a(13) =91144a(14) =325878a(15) =1174281a(16) =4260282a(17) =15548694a(18) =57048048a(19) =210295326a(20) =778483932a(21) =2892818244a(22) =10786724388a(23) =40347919626a(24) =151355847012a(25) =569274150156
External references
- oeis: A000957