Number of planted trees where non-root, non-leaf nodes an even distance from root are of degree 2.

Terms

a(0) =1a(1) =1a(2) =1a(3) =2a(4) =3a(5) =6a(6) =10a(7) =20a(8) =36a(9) =72a(10) =137a(11) =275a(12) =541a(13) =1098a(14) =2208a(15) =4521a(16) =9240a(17) =19084a(18) =39451a(19) =82113a(20) =171240a(21) =358794a(22) =753460a(23) =1587740a(24) =3353192a(25) =7100909a(26) =15067924a(27) =32044456a(28) =68272854a(29) =145730675