Number of 4-tuples (w,x,y,z) with all terms in {1,...,n} and w*x>2*y*z.

Terms

a(0) =0a(1) =0a(2) =1a(3) =15a(4) =55a(5) =156a(6) =338a(7) =666a(8) =1159a(9) =1905a(10) =2950a(11) =4399a(12) =6275a(13) =8748a(14) =11847a(15) =15721a(16) =20450a(17) =26228a(18) =33078a(19) =41271a(20) =50799a(21) =61947a(22) =74832a(23) =89674a(24) =106480a(25) =125659a(26) =147291a(27) =171618a(28) =198767a(29) =229139