A binomial coefficient sum.

Terms

a(0) =1a(1) =1a(2) =2a(3) =9a(4) =36a(5) =190a(6) =980a(7) =5705a(8) =33040a(9) =204876a(10) =1268568a(11) =8209278a(12) =53105976a(13) =354331692a(14) =2364239592a(15) =16140234825a(16) =110206067400a(17) =765868074400