Column 3 of triangle A130580.

Terms

a(0) =1a(1) =1a(2) =4a(3) =10a(4) =26a(5) =71a(6) =210a(7) =673a(8) =2328a(9) =8649a(10) =34341a(11) =145043a(12) =648895a(13) =3063357a(14) =15208948a(15) =79172266a(16) =430976971a(17) =2447365652a(18) =14466697028a(19) =88841985950a(20) =565817585424