Number of nondecreasing integer sequences of length 28 with sum zero and sum of absolute values 2n.

Terms

a(0) =1a(1) =4a(2) =9a(3) =25a(4) =49a(5) =121a(6) =225a(7) =484a(8) =900a(9) =1764a(10) =3136a(11) =5929a(12) =10201a(13) =18225a(14) =30973a(15) =53343a(16) =88135a(17) =147976a(18) =239366a(19) =391166a(20) =622410a(21) =992731a(22) =1550288a(23) =2428726a(24) =3729389a(25) =5730799a(26) =8676276a(27) =13115757a(28) =19565503a(29) =29154058