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

Terms

a(0) =0a(1) =0a(2) =7a(3) =33a(4) =96a(5) =241a(6) =498a(7) =933a(8) =1579a(9) =2520a(10) =3828a(11) =5578a(12) =7866a(13) =10815a(14) =14509a(15) =19044a(16) =24603a(17) =31294a(18) =39255a(19) =48645a(20) =59599a(21) =72345a(22) =87051a(23) =103897a(24) =123060a(25) =144792a(26) =169291a(27) =196776a(28) =227445a(29) =261580