A diagonal of A059438.

Terms

a(0) =0a(1) =0a(2) =1a(3) =2a(4) =7a(5) =32a(6) =177a(7) =1142a(8) =8411a(9) =69692a(10) =642581a(11) =6534978a(12) =72754927a(13) =880877928a(14) =11530686953a(15) =162331760494