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

Terms

a(0) =0a(1) =0a(2) =2a(3) =10a(4) =36a(5) =92a(6) =202a(7) =386a(8) =680a(9) =1112a(10) =1730a(11) =2570a(12) =3692a(13) =5140a(14) =6986a(15) =9282a(16) =12112a(17) =15536a(18) =19650a(19) =24522a(20) =30260a(21) =36940a(22) =44682a(23) =53570a(24) =63736a(25) =75272a(26) =88322a(27) =102986a(28) =119420a(29) =137732