Number of nondecreasing integer sequences of length 12 with sum zero and sum of absolute values 2n.

Terms

a(0) =1a(1) =4a(2) =9a(3) =25a(4) =49a(5) =121a(6) =222a(7) =466a(8) =828a(9) =1537a(10) =2546a(11) =4506a(12) =7097a(13) =11656a(14) =17964a(15) =28080a(16) =41533a(17) =62829a(18) =90245a(19) =131868a(20) =185633a(21) =262931a(22) =361620a(23) =502438a(24) =677292a(25) =919091a(26) =1221175a(27) =1627409a(28) =2126641a(29) =2793158