Frequency of n-th largest distance in N times N grid, N > n.

Terms

a(0) =2a(1) =8a(2) =12a(3) =8a(4) =16a(5) =24a(6) =20a(7) =32a(8) =18a(9) =24a(10) =40a(11) =48a(12) =28a(13) =48a(14) =60a(15) =32a(16) =32a(17) =56a(18) =72a(19) =80a(20) =36a(21) =64a(22) =84a(23) =96a(24) =50a(25) =40a(26) =72a(27) =96a(28) =112a(29) =120