Number of nondecreasing integer sequences of length 11 with sum zero and sum of absolute values 2n.

Terms

a(0) =1a(1) =4a(2) =9a(3) =25a(4) =49a(5) =120a(6) =217a(7) =446a(8) =773a(9) =1408a(10) =2279a(11) =3955a(12) =6073a(13) =9760a(14) =14692a(15) =22467a(16) =32445a(17) =48073a(18) =67444a(19) =96568a(20) =132921a(21) =184487a(22) =248245a(23) =338391a(24) =446533a(25) =594557a(26) =774198a(27) =1012918a(28) =1297749a(29) =1674816