|
Search: id:A115223
|
|
|
| A115223 |
|
Number of 3 X 3 symmetric matrices over Z(n) having determinant 0. |
|
+0
2
|
|
| 1, 36, 261, 1408, 3225, 9396, 17101, 47104, 76545, 116100, 162261, 367488, 373321, 615636, 841725, 1638400, 1424481, 2755620, 2482597, 4540800, 4463361, 5841396, 6447981, 12294144, 11640625, 13439556, 18954729, 24078208, 20534697, 30302100
(list; graph; listen)
|
|
|
OFFSET
|
1,2
|
|
|
FORMULA
|
a(n)=n^6-A115225(n). For prime n, a(n)=(n^3+n-1)n^2.
|
|
MATHEMATICA
|
Table[cnt=0; Do[m={{a, b, c}, {b, d, e}, {c, e, f}}; If[Det[m, Modulus->n]==0, cnt++ ], {a, 0, n-1}, {b, 0, n-1}, {c, 0, n-1}, {d, 0, n-1}, {e, 0, n-1}, {f, 0, n-1}]; cnt, {n, 2, 20}]
|
|
CROSSREFS
|
Cf. A115221 (number of 3 X 3 matrices over Z(n) having determinant 0).
Sequence in context: A017342 A115332 A133072 this_sequence A135181 A014136 A091081
Adjacent sequences: A115220 A115221 A115222 this_sequence A115224 A115225 A115226
|
|
KEYWORD
|
mult,nonn
|
|
AUTHOR
|
T. D. Noe (noe(AT)sspectra.com), Jan 16 2006
|
|
|
Search completed in 0.002 seconds
|
