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) =5a(3) =23a(4) =79a(5) =188a(6) =402a(7) =742a(8) =1283a(9) =2059a(10) =3164a(11) =4633a(12) =6615a(13) =9112a(14) =12299a(15) =16253a(16) =21114a(17) =26924a(18) =33932a(19) =42161a(20) =51885a(21) =63153a(22) =76182a(23) =91068a(24) =108172a(25) =127453a(26) =149257a(27) =173726a(28) =201163a(29) =231591