A restricted class of multiple edge-free maps on n edges.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =5a(5) =13a(6) =48a(7) =160a(8) =578a(9) =2078a(10) =7658a(11) =28467a(12) =107096a(13) =406290a(14) =1553570a(15) =5980040a(16) =23154950a(17) =90124865a(18) =352423336a(19) =1383872558a(20) =5454586036a(21) =21572961498a(22) =85587023964a(23) =340518976173