a(n) = 2*A010844(n) + 1.

Terms

a(0) =3a(1) =7a(2) =27a(3) =159a(4) =1267a(5) =12663a(6) =151947a(7) =2127247a(8) =34035939a(9) =612646887a(10) =12252937723a(11) =269564629887