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) =6a(3) =22a(4) =54a(5) =106a(6) =184a(7) =292a(8) =436a(9) =620a(10) =850a(11) =1130a(12) =1466a(13) =1862a(14) =2324a(15) =2856a(16) =3464a(17) =4152a(18) =4926a(19) =5790a(20) =6750a(21) =7810a(22) =8976a(23) =10252a(24) =11644a(25) =13156a(26) =14794a(27) =16562a(28) =18466a(29) =20510