Triangle of subsequences of A140825 with a mirror symmetry.

Terms

a(0) =-1a(1) =1a(2) =-1a(3) =-19a(4) =11a(5) =-19a(6) =27a(7) =-11a(8) =11a(9) =-27a(10) =-863a(11) =271a(12) =-191a(13) =271a(14) =-863a(15) =1375a(16) =-351a(17) =191a(18) =-191a(19) =351a(20) =-1375a(21) =-33953a(22) =7297a(23) =-3233a(24) =2497a(25) =-3233a(26) =7297a(27) =-33953