Number of (w,x,y) with all terms in {0,...,n} and 2|w-x| >= max(w,x,y)-min(w,x,y).

Terms

a(0) =1a(1) =6a(2) =21a(3) =48a(4) =93a(5) =158a(6) =249a(7) =368a(8) =521a(9) =710a(10) =941a(11) =1216a(12) =1541a(13) =1918a(14) =2353a(15) =2848a(16) =3409a(17) =4038a(18) =4741a(19) =5520a(20) =6381a(21) =7326a(22) =8361a(23) =9488a(24) =10713a(25) =12038a(26) =13469a(27) =15008a(28) =16661a(29) =18430