Number of nondecreasing integer sequences of length 9 with sum zero and sum of absolute values 2n.

Terms

a(0) =1a(1) =4a(2) =9a(3) =25a(4) =48a(5) =113a(6) =189a(7) =367a(8) =598a(9) =1031a(10) =1559a(11) =2566a(12) =3681a(13) =5593a(14) =7926a(15) =11480a(16) =15598a(17) =21984a(18) =29080a(19) =39672a(20) =51688a(21) =68384a(22) =87284a(23) =113869a(24) =142723a(25) =181944a(26) =225921a(27) =283427a(28) =346610a(29) =430023