Second column of triangle in A099964.

Terms

a(0) =1a(1) =2a(2) =3a(3) =6a(4) =14a(5) =31a(6) =78a(7) =235a(8) =665a(9) =1926a(10) =5886a(11) =21832a(12) =75333a(13) =266377a(14) =933842a(15) =3422282a(16) =14954936a(17) =61055379a(18) =254751651a(19) =1054728818a(20) =4378056288a(21) =18699691530a(22) =94021272519a(23) =443332334411