Main diagonal of A276554.

Terms

a(0) =1a(1) =-1a(2) =-3a(3) =8a(4) =13a(5) =-51a(6) =-120a(7) =538a(8) =781a(9) =-5419a(10) =-3053a(11) =47673a(12) =5080a(13) =-427740a(14) =136462a(15) =3922383a(16) =-3278067a(17) =-34819588a(18) =48561567a(19) =299316651a(20) =-603368637a(21) =-2509708844a(22) =6948730643a(23) =20210062532a(24) =-76150197416a(25) =-152569240051a(26) =801154765564