Number of 0..n arrays x(0..3) of 4 elements with nondecreasing average value.

Terms

a(0) =5a(1) =19a(2) =51a(3) =113a(4) =219a(5) =388a(6) =638a(7) =995a(8) =1483a(9) =2133a(10) =2975a(11) =4047a(12) =5383a(13) =7028a(14) =9022a(15) =11415a(16) =14253a(17) =17593a(18) =21485a(19) =25993a(20) =31173a(21) =37094a(22) =43818a(23) =51421a(24) =59969a(25) =69545a(26) =80221a(27) =92085a(28) =105215a(29) =119706