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) =8a(3) =46a(4) =152a(5) =378a(6) =792a(7) =1476a(8) =2528a(9) =4060a(10) =6200a(11) =9090a(12) =12888a(13) =17766a(14) =23912a(15) =31528a(16) =40832a(17) =52056a(18) =65448a(19) =81270a(20) =99800a(21) =121330a(22) =146168a(23) =174636a(24) =207072a(25) =243828a(26) =285272a(27) =331786a(28) =383768a(29) =441630