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

Terms

a(0) =0a(1) =0a(2) =2a(3) =24a(4) =98a(5) =272a(6) =608a(7) =1184a(8) =2092a(9) =3440a(10) =5350a(11) =7960a(12) =11422a(13) =15904a(14) =21588a(15) =28672a(16) =37368a(17) =47904a(18) =60522a(19) =75480a(20) =93050a(21) =113520a(22) =137192a(23) =164384a(24) =195428a(25) =230672a(26) =270478a(27) =315224a(28) =365302a(29) =421120