Sum of the 2 X 2 minors in the n X n Pascal matrix.

Terms

a(0) =0a(1) =0a(2) =1a(3) =7a(4) =34a(5) =144a(6) =574a(7) =2226a(8) =8533a(9) =32587a(10) =124453a(11) =476145a(12) =1826175a(13) =7022379a(14) =27072487a(15) =104614863a(16) =405122290a(17) =1571859864a(18) =6109296442a(19) =23781666198a(20) =92704406320a(21) =361832294964