Total number of leaves and degree-1 roots in the rooted trees of order n.

Terms

a(0) =0a(1) =2a(2) =4a(3) =10a(4) =26a(5) =67a(6) =180a(7) =482a(8) =1319a(9) =3627a(10) =10082a(11) =28150a(12) =79142a(13) =223309a(14) =632805a(15) =1798614a(16) =5127257a(17) =14650352a(18) =41952791a(19) =120358095a(20) =345878470a(21) =995441814a(22) =2868762513a(23) =8277505162a(24) =23910288016a(25) =69136464102a(26) =200092471111a(27) =579592538321