Triangle read by rows: characteristic polynomials of certain matrices, see Mathematica program.

Terms

a(0) =3a(1) =3a(2) =-1a(3) =8a(4) =-6a(5) =1a(6) =20a(7) =-24a(8) =9a(9) =-1a(10) =45a(11) =-84a(12) =50a(13) =-12a(14) =1a(15) =125a(16) =-275a(17) =225a(18) =-85a(19) =15a(20) =-1a(21) =320a(22) =-864a(23) =900a(24) =-468a(25) =129a(26) =-18a(27) =1a(28) =845a(29) =-2639