Main diagonal of A291701.

Terms

a(0) =1a(1) =-1a(2) =1a(3) =-4a(4) =13a(5) =-36a(6) =100a(7) =-281a(8) =797a(9) =-2281a(10) =6546a(11) =-18778a(12) =53872a(13) =-154662a(14) =444263a(15) =-1276284a(16) =3665773a(17) =-10524939a(18) =30203731a(19) =-86624174a(20) =248257298a(21) =-710882708a(22) =2033663952a(23) =-5811660425a(24) =16588828304a(25) =-47291077636a(26) =134630218334a(27) =-382697080366