Diagonal sums of a scaled Legendre triangle.

Terms

a(0) =1a(1) =0a(2) =-1a(3) =2a(4) =11a(5) =12a(6) =19a(7) =174a(8) =1073a(9) =6584a(10) =45871a(11) =337098a(12) =2563293a(13) =20346204a(14) =169904575a(15) =1501012310a(16) =14065496355a(17) =139601710224