Number of nondecreasing arrangements of 4 numbers in -(n+2)..(n+2) with sum zero.

Terms

a(0) =18a(1) =33a(2) =55a(3) =86a(4) =126a(5) =177a(6) =241a(7) =318a(8) =410a(9) =519a(10) =645a(11) =790a(12) =956a(13) =1143a(14) =1353a(15) =1588a(16) =1848a(17) =2135a(18) =2451a(19) =2796a(20) =3172a(21) =3581a(22) =4023a(23) =4500a(24) =5014a(25) =5565a(26) =6155a(27) =6786a(28) =7458a(29) =8173