(A192466)/2.

Terms

a(0) =1a(1) =3a(2) =12a(3) =45a(4) =176a(5) =693a(6) =2752a(7) =10965a(8) =43776a(9) =174933a(10) =699392a(11) =2796885a(12) =11186176a(13) =44741973a(14) =178962432a(15) =715838805a(16) =2863333376a(17) =11453289813a(18) =45813071872a(19) =183252112725a(20) =733008101376