a(n) = -A001353(n).

Terms

a(0) =0a(1) =-1a(2) =-4a(3) =-15a(4) =-56a(5) =-209a(6) =-780a(7) =-2911a(8) =-10864a(9) =-40545a(10) =-151316a(11) =-564719a(12) =-2107560a(13) =-7865521a(14) =-29354524a(15) =-109552575a(16) =-408855776a(17) =-1525870529a(18) =-5694626340a(19) =-21252634831a(20) =-79315912984a(21) =-296011017105