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a(n) = 4^(n^2 - n).
8

%I #17 Sep 13 2023 11:17:23

%S 1,1,16,4096,16777216,1099511627776,1152921504606846976,

%T 19342813113834066795298816,5192296858534827628530496329220096,

%U 22300745198530623141535718272648361505980416

%N a(n) = 4^(n^2 - n).

%C Number of nilpotent n X n matrices over GF(4).

%C (-1)^n * resultant of the Chebyshev polynomial of first kind of degree n and Chebyshev polynomial of first kind of degree 2n (cf. A039991). - _Benoit Cloitre_, Jan 26 2003

%C a(n) is the number of spanning subgraphs (or equivalently sets of edges) in the n X n grid graph. - _Andrew Howroyd_, Jan 29 2023

%D N. J. Fine and I. N. Herstein, The probability that a matrix be nilpotent, Illinois J. Math., 2 (1958), 499-504.

%D M. Gerstenhaber, On the number of nilpotent matrices with coefficients in a finite field. Illinois J. Math., Vol. 5 (1961), 330-333.

%H Andrew Howroyd, <a href="/A053765/b053765.txt">Table of n, a(n) for n = 0..40</a>

%o (PARI) a(n) = 4^(n^2 - n) \\ _Andrew Howroyd_, Jan 29 2023

%Y Cf. A053763, A053764.

%K easy,nonn

%O 0,3

%A _Stephen G Penrice_, Mar 29 2000

%E More terms from _James A. Sellers_, Apr 08 2000