a(n) = A000129(n) * A000129(n+1)/2.

Terms

a(0) =0a(1) =1a(2) =5a(3) =30a(4) =174a(5) =1015a(6) =5915a(7) =34476a(8) =200940a(9) =1171165a(10) =6826049a(11) =39785130a(12) =231884730a(13) =1351523251a(14) =7877254775a(15) =45912005400a(16) =267594777624