Number of (w,x,y,z) with all terms in {0,...,n} and |w-x|<=|x-y|<=|y-z|.

Terms

a(0) =1a(1) =8a(2) =35a(3) =94a(4) =209a(5) =398a(6) =697a(7) =1130a(8) =1743a(9) =2568a(10) =3661a(11) =5060a(12) =6833a(13) =9024a(14) =11711a(15) =14946a(16) =18817a(17) =23382a(18) =28741a(19) =34958a(20) =42143a(21) =50368a(22) =59753a(23) =70376a(24) =82369a(25) =95816a(26) =110859a(27) =127590a(28) =146161a(29) =166670