Number of (w,x,y,z) with all terms in {1,...,n} and w<2x+y+z.

Terms

a(0) =0a(1) =1a(2) =16a(3) =81a(4) =255a(5) =621a(6) =1285a(7) =2377a(8) =4050a(9) =6481a(10) =9870a(11) =14441a(12) =20441a(13) =28141a(14) =37835a(15) =49841a(16) =64500a(17) =82177a(18) =103260a(19) =128161a(20) =157315a(21) =191181a(22) =230241a(23) =275001a(24) =325990a(25) =383761a(26) =448890a(27) =521977a(28) =603645a(29) =694541