a(n) = A053141(n)/2.

Terms

a(0) =0a(1) =1a(2) =7a(3) =42a(4) =246a(5) =1435a(6) =8365a(7) =48756a(8) =284172a(9) =1656277a(10) =9653491a(11) =56264670a(12) =327934530a(13) =1911342511a(14) =11140120537a(15) =64929380712a(16) =378436163736