a(n) = A352682(n, n).

Terms

a(0) =1a(1) =1a(2) =3a(3) =11a(4) =42a(5) =176a(6) =808a(7) =4015a(8) =21423a(9) =122035a(10) =738424a(11) =4725200a(12) =31854056a(13) =225472729a(14) =1670849235a(15) =12929089547a(16) =104227219082a(17) =873524820380