Sequence with a (1,-1) Somos-4 Hankel transform.

Terms

a(0) =1a(1) =0a(2) =1a(3) =1a(4) =4a(5) =12a(6) =42a(7) =147a(8) =527a(9) =1914a(10) =7039a(11) =26159a(12) =98110a(13) =370919a(14) =1412211a(15) =5410273a(16) =20841886a(17) =80685792a(18) =313747624a(19) =1224895416a(20) =4799435482a(21) =18867423751a(22) =74394859297a(23) =294152650731