Sequence arising in search for Legendre sequences.

Terms

a(0) =1a(1) =2a(2) =1a(3) =6a(4) =11a(5) =10a(6) =43a(7) =74a(8) =109a(9) =207a(10) =562a(11) =770a(12) =1647a(13) =3546a(14) =5654a(15) =5475a(16) =19513a(17) =23236a(18) =54896