A007318 * A100071.

Terms

a(0) =1a(1) =3a(2) =11a(3) =37a(4) =123a(5) =401a(6) =1293a(7) =4131a(8) =13107a(9) =41353a(10) =129873a(11) =406319a(12) =1267093a(13) =3940431a(14) =12224579a(15) =37845117a(16) =116944371a(17) =360771417a(18) =1111332129a(19) =3418840431a(20) =10504903809a(21) =32242682787a(22) =98863833159a(23) =302863592073a(24) =927025884477