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

Terms

a(0) =0a(1) =1a(2) =11a(3) =33a(4) =76a(5) =144a(6) =262a(7) =415a(8) =655a(9) =959a(10) =1377a(11) =1886a(12) =2610a(13) =3396a(14) =4465a(15) =5689a(16) =7169a(17) =8883a(18) =11042a(19) =13334a(20) =16240a(21) =19355a(22) =23003a(23) =27059a(24) =31892a(25) =36952a(26) =42878a(27) =49384a(28) =56659a(29) =64471