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

Terms

a(0) =0a(1) =1a(2) =14a(3) =57a(4) =158a(5) =353a(6) =688a(7) =1217a(8) =2004a(9) =3121a(10) =4650a(11) =6681a(12) =9314a(13) =12657a(14) =16828a(15) =21953a(16) =28168a(17) =35617a(18) =44454a(19) =54841a(20) =66950a(21) =80961a(22) =97064a(23) =115457a(24) =136348a(25) =159953a(26) =186498a(27) =216217a(28) =249354a(29) =286161