Numbers of the form 4u+2 in A351551.

Terms

a(0) =2a(1) =10a(2) =34a(3) =106a(4) =1666a(5) =8746a(6) =26242a(7) =134946a(8) =2125762a(9) =3997714a(10) =8298346a(11) =156057642a(12) =323814834a(13) =672166026a(14) =3901441050