Related to Fibonacci numbers.

Terms

a(0) =1a(1) =3a(2) =14a(3) =60a(4) =279a(5) =1251a(6) =5329a(7) =21532a(8) =83225a(9) =310464a(10) =1126502a(11) =4000602a(12) =13973725a(13) =48187521a(14) =164535708a(15) =557528652a(16) =1878067349a(17) =6297614277a(18) =21043287325a(19) =70125062642a(20) =233198372319a(21) =774246922848