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

Terms

a(0) =0a(1) =0a(2) =4a(3) =24a(4) =88a(5) =230a(6) =504a(7) =966a(8) =1696a(9) =2772a(10) =4300a(11) =6380a(12) =9144a(13) =12714a(14) =17248a(15) =22890a(16) =29824a(17) =38216a(18) =48276a(19) =60192a(20) =74200a(21) =90510a(22) =109384a(23) =131054a(24) =155808a(25) =183900a(26) =215644a(27) =251316a(28) =291256a(29) =335762