Number of (w,x,y,z) with all terms in {1,...,n} and w<x+y+z.

Terms

a(0) =0a(1) =1a(2) =16a(3) =80a(4) =251a(5) =610a(6) =1261a(7) =2331a(8) =3970a(9) =6351a(10) =9670a(11) =14146a(12) =20021a(13) =27560a(14) =37051a(15) =48805a(16) =63156a(17) =80461a(18) =101100a(19) =125476a(20) =154015a(21) =187166a(22) =225401a(23) =269215a(24) =319126a(25) =375675a(26) =439426a(27) =510966a(28) =590905a(29) =679876