Number of length-4 0..n arrays with no repeated value greater than the previous repeated value.

Terms

a(0) =15a(1) =78a(2) =250a(3) =615a(4) =1281a(5) =2380a(6) =4068a(7) =6525a(8) =9955a(9) =14586a(10) =20670a(11) =28483a(12) =38325a(13) =50520a(14) =65416a(15) =83385a(16) =104823a(17) =130150a(18) =159810a(19) =194271a(20) =234025a(21) =279588a(22) =331500a(23) =390325a(24) =456651a(25) =531090a(26) =614278a(27) =706875a(28) =809565a(29) =923056