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

Terms

a(0) =0a(1) =0a(2) =1a(3) =1a(4) =14a(5) =18a(6) =31a(7) =35a(8) =80a(9) =96a(10) =125a(11) =133a(12) =216a(13) =228a(14) =269a(15) =309a(16) =444a(17) =460a(18) =543a(19) =559a(20) =720a(21) =784a(22) =853a(23) =873a(24) =1142a(25) =1202a(26) =1287a(27) =1363a(28) =1596a(29) =1624