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

Terms

a(0) =0a(1) =1a(2) =16a(3) =78a(4) =240a(5) =577a(6) =1182a(7) =2172a(8) =3680a(9) =5865a(10) =8900a(11) =12986a(12) =18336a(13) =25193a(14) =33810a(15) =44472a(16) =57472a(17) =73137a(18) =91800a(19) =113830a(20) =139600a(21) =169521a(22) =204006a(23) =243508a(24) =288480a(25) =339417a(26) =396812a(27) =461202a(28) =533120a(29) =613145