%I A069480
%S A069480 1,2,5,6,13,12,25,20,41,30,61,42,85,56,113,72,145,90,181,110,221,132,
%T A069480 265,156,313,182,365,210,421,240,481,272,545,306,613,342,685,380,761,
%U A069480 420,841,462,925,506,1013,552,1105,600,1201,650,1301,702,1405,756,1513
%V A069480 1,-2,-5,6,13,-12,-25,20,41,-30,-61,42,85,-56,-113,72,145,-90,-181,110,
               221,-132,-265,
%W A069480 156,313,-182,-365,210,421,-240,-481,272,545,-306,-613,342,685,-380,-761,
               420,841,-462,
%X A069480 -925,506,1013,-552,-1105,600,1201,-650,-1301,702,1405,-756,-1513
%N A069480 Determinant of rank n matrix of 1..n^2 filled successively along antidiagonals.
%C A069480 The sorted absolute values of this sequence begin: 1, 2, 5, 6, 12, 13, 
               20, 25, 30, 41, 42, 56, 61, 72, 85, 90, 110, 113, 132, 145, 156, 
               181, 182,
%D A069480 On comp.soft-sys.math.mathematica (Mar 20 2002) Diamond Mark. R. asked 
               for a nice way to generate matrices 'along the diagonals' of the 
               form (see example). The coding is via Wouter Meeussen (wouter.meeussen(AT)pandora.be)
%F A069480 a(n) = n*(n+2)/4, n = 0 mod 4; (n^2+1)/2, n = 1 mod 4; -n*(n+2)/4, n 
               = 2 mod 4; -(n^2+1)/2, n = 3 mod 4; g.f. is x (x^4 - 2 x^2 - 2 x 
               + 1) / (x^2 + 1)^3
%e A069480 a(4) = 6 = 4*6/4 = |1 3 6 10 | 2 5 9 13 | 4 8 12 15 | 7 11 14 16|.
%t A069480 f[n_] := Table[(i + j - 1)((i + j - 1) - 1)/2 + 1 + (j - 1) - Mod[i + 
               j - 1, n, 1]^2 Quotient[i + j - 1, n, 1], {i, n}, {j, n}]; Table[ 
               Det[ f[n]], {n, 1, 50}]
%Y A069480 Sequence in context: A064765 A082552 A057683 this_sequence A100613 A070911 
               A113240
%Y A069480 Adjacent sequences: A069477 A069478 A069479 this_sequence A069481 A069482 
               A069483
%K A069480 easy,sign
%O A069480 1,2
%A A069480 Robert G. Wilson v (rgwv(AT)rgwv.com) and Marc LeBrun (mlb(AT)well.com), 
               Mar 26 2002