A011787 Number of n X n matrices over Z_4 whose determinant is 1.

1, 48, 43008, 660602880, 167761422581760, 692647993190048071680, 46119672943810238272430407680, 49327181820263339694887026906732953600, 845779385319367513935228608424336170436211507200, 232259029997997019092189603223864660200729932409175906713600

Offset: 1

Author

Benjamin T. Love (benlove(AT)preston.polaristel.net)

Keywords

• nonn

Crossrefs

Cf. A048651, A065128.

Programs

Mathematica

a[n_] := 2^(2*n^2-1) * Product[1 - 1/2^k, {k, 1, n}]; Array[a, 10] (* Amiram Eldar, Jul 12 2025 *)

PARI

a(n) = 2^(2*n^2-1) * prod(k = 1, n, 1-1/2^k); \\ Amiram Eldar, Jul 12 2025

Formula

a(n) = A065128(n)/2.

a(n) ~ c * 4^(n^2), where c = A048651 / 2. - Amiram Eldar, Jul 12 2025

Extensions

More terms from Max Alekseyev, Jan 22 2012