This is a front-end for the Online Encyclopedia of Integer Sequences, made by Christian Perfect. The idea is to provide OEIS entries in non-ancient HTML, and then to think about how they're presented visually. The source code is on GitHub.
%I A011787 #14 Jul 12 2025 08:35:37
%S A011787 1,48,43008,660602880,167761422581760,692647993190048071680,
%T A011787 46119672943810238272430407680,49327181820263339694887026906732953600,
%U A011787 845779385319367513935228608424336170436211507200,232259029997997019092189603223864660200729932409175906713600
%N A011787 Number of n X n matrices over Z_4 whose determinant is 1.
%F A011787 a(n) = A065128(n)/2.
%F A011787 a(n) ~ c * 4^(n^2), where c = A048651 / 2. - _Amiram Eldar_, Jul 12 2025
%t A011787 a[n_] := 2^(2*n^2-1) * Product[1 - 1/2^k, {k, 1, n}]; Array[a, 10] (* _Amiram Eldar_, Jul 12 2025 *)
%o A011787 (PARI) a(n) = 2^(2*n^2-1) * prod(k = 1, n, 1-1/2^k); \\ _Amiram Eldar_, Jul 12 2025
%Y A011787 Cf. A048651, A065128.
%K A011787 nonn
%O A011787 1,2
%A A011787 Benjamin T. Love (benlove(AT)preston.polaristel.net)
%E A011787 More terms from _Max Alekseyev_, Jan 22 2012