Number of distinct products i*j*k*l for 1 <= i < j < k < l <= n.

Terms

a(0) =0a(1) =0a(2) =0a(3) =1a(4) =5a(5) =13a(6) =29a(7) =50a(8) =79a(9) =111a(10) =186a(11) =219a(12) =345a(13) =428a(14) =513a(15) =610a(16) =884a(17) =991a(18) =1387a(19) =1535a(20) =1742a(21) =1994a(22) =2671a(23) =2833a(24) =3319a(25) =3719a(26) =4154a(27) =4474a(28) =5751a(29) =5985