Number of (w,x,y,z) with all terms in {1,...,n} and w*x < 2*y*z.

Terms

a(0) =0a(1) =1a(2) =11a(3) =58a(4) =177a(5) =437a(6) =894a(7) =1659a(8) =2813a(9) =4502a(10) =6836a(11) =10008a(12) =14121a(13) =19449a(14) =26117a(15) =34372a(16) =44422a(17) =56597a(18) =71044a(19) =88160a(20) =108115a(21) =131328a(22) =158074a(23) =188773a(24) =223604a(25) =263172a(26) =307719a(27) =357715a(28) =413493a(29) =475690