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

Terms

a(0) =1a(1) =5a(2) =15a(3) =37a(4) =77a(5) =138a(6) =223a(7) =338a(8) =489a(9) =679a(10) =911a(11) =1191a(12) =1525a(13) =1916a(14) =2367a(15) =2884a(16) =3473a(17) =4137a(18) =4879a(19) =5705a(20) =6621a(21) =7630a(22) =8735a(23) =9942a(24) =11257a(25) =12683a(26) =14223a(27) =15883a(28) =17669a(29) =19584