Number of nondecreasing integer sequences of length 23 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) =5928a(12) =10193a(13) =18187a(14) =30837a(15) =52927a(16) =87006a(17) =145175a(18) =232959a(19) =377356a(20) =594285a(21) =937587a(22) =1446300a(23) =2237439a(24) =3387772a(25) =5131822a(26) =7650285a(27) =11384216a(28) =16699632a(29) =24466949