Third column sequence of unsigned triangle A056588.

Terms

a(0) =1a(1) =4a(2) =16a(3) =53a(4) =166a(5) =492a(6) =1413a(7) =3960a(8) =10912a(9) =29689a(10) =80026a(11) =214196a(12) =570289a(13) =1512300a(14) =3998160a(15) =10545741a(16) =27766942a(17) =73012060a(18) =191785165a(19) =503378480a(20) =1320425536a(21) =3462057009a(22) =9074076786a(23) =23776857828a(24) =62289901081a(25) =163159711492