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

Terms

a(0) =0a(1) =0a(2) =2a(3) =8a(4) =22a(5) =46a(6) =84a(7) =138a(8) =212a(9) =308a(10) =430a(11) =580a(12) =762a(13) =978a(14) =1232a(15) =1526a(16) =1864a(17) =2248a(18) =2682a(19) =3168a(20) =3710a(21) =4310a(22) =4972a(23) =5698a(24) =6492a(25) =7356a(26) =8294a(27) =9308a(28) =10402a(29) =11578