A211054 - OEIS

%I #10 Jan 11 2017 01:32:29

%S 0,1,2,6,11,26,27,66,57,109,109,182,129,319,187,332,360,497,309,714,

%T 397,839,690,842,571,1456,821,1156,1126,1663,907,2264,1071,2106,1708,

%U 1976,1798,3449,1513,2474,2358,3874,1839,4372,2065,3973

%N Number of 2 X 2 matrices having all terms in {1,...,n} and determinant n-1.

%C For a guide to related sequences, see A210000.

%H Chai Wah Wu, <a href="/A211054/b211054.txt">Table of n, a(n) for n = 0..3000</a>

%e A(2) counts these matrices:

%e 1 1.....2 1

%e 1 2.....1 1

%t a = 1; b = n; z1 = 45;

%t t[n_] := t[n] = Flatten[Table[w*z - x*y, {w, a, b}, {x, a, b}, {y, a, b}, {z, a, b}]]

%t c[n_, k_] := c[n, k] = Count[t[n], k]

%t Table[c[n, n - 1], {n, 1, z1}]  (* A211054 *)

%Y Cf. A210000, A211053.

%K nonn

%O 0,3

%A _Clark Kimberling_, Mar 31 2012

%E Offset corrected by _Chai Wah Wu_, Jan 04 2017