|
Search: id:A115077
|
|
|
| A115077 |
|
Number of 2 X 2 symmetric matrices over Z(n) having nonzero determinant. |
|
+0
3
|
|
| 0, 4, 18, 44, 100, 180, 294, 432, 630, 900, 1210, 1548, 2028, 2548, 3150, 3744, 4624, 5436, 6498, 7500, 8820, 10164, 11638, 13104, 14900, 16900, 18792, 20972, 23548, 26100, 28830, 31360, 34848, 38148, 41650, 44676, 49284, 53428, 57798, 62000
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
FORMULA
|
a(n)=n^3-A115075(n). For squarefree n, a(n)=(n-1)n^2.
|
|
MATHEMATICA
|
Table[cnt=0; Do[m={{a, b}, {b, c}}; If[Det[m, Modulus->n]>0, cnt++ ], {a, 0, n-1}, {b, 0, n-1}, {c, 0, n-1}]; cnt, {n, 50}]
|
|
CROSSREFS
|
Cf. A005353 (number of 2 X 2 matrices over Z(n) having nonzero determinant).
Sequence in context: A062235 A126283 A023618 this_sequence A066153 A023650 A163188
Adjacent sequences: A115074 A115075 A115076 this_sequence A115078 A115079 A115080
|
|
KEYWORD
|
nonn
|
|
AUTHOR
|
T. D. Noe (noe(AT)sspectra.com), Jan 12 2006
|
|
|
Search completed in 0.002 seconds
|
