Second column of triangle in A099961.

Terms

a(0) =1a(1) =2a(2) =3a(3) =5a(4) =10a(5) =23a(6) =51a(7) =128a(8) =386a(9) =1092a(10) =3370a(11) =12458a(12) =43037a(13) =158638a(14) =691999a(15) =2827035a(16) =12150430a(17) =60980759a(18) =287737037a(19) =1414689552a(20) =8021603122a(21) =42939104470a(22) =237864297110