Diagonal sums of number triangle A109956.

Terms

a(0) =1a(1) =-1a(2) =4a(3) =-16a(4) =74a(5) =-368a(6) =1926a(7) =-10455a(8) =58333a(9) =-332489a(10) =1927761a(11) =-11334128a(12) =67416570a(13) =-404956315a(14) =2453012916a(15) =-14967587873a(16) =91910798556a(17) =-567566697627