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 A060870 #20 Dec 26 2024 13:21:45
%S A060870 4,144,3844,97344,2439844,61027344,1525839844,38146777344,
%T A060870 953673339844,23841853027344,596046423339844,14901161071777344,
%U A060870 372529029235839844,9313225743103027344,232830643638610839844,5820766091270446777344,145519152283287048339844,3637978807089805603027344
%N A060870 Number of n X n matrices over GF(5) with rank 1.
%H A060870 Harry J. Smith, <a href="/A060870/b060870.txt">Table of n, a(n) for n = 1..200</a>
%H A060870 <a href="/index/Rec#order_03">Index entries for linear recurrences with constant coefficients</a>, signature (31,-155,125).
%F A060870 a(n) = 1/4 * (5^n - 1)^2.
%F A060870 G.f.: -4*x*(5*x+1) / ((x-1)*(5*x-1)*(25*x-1)). [_Colin Barker_, Dec 23 2012]
%e A060870 a(2) = 144 because there are 145 (the second element in sequence A060720) singular 2 X 2 matrices over GF(5), that have rank <= 1 of which only the zero matrix has rank zero so a(2) = 145 - 1 = 144.
%t A060870 Table[(5^n-1)^2/4,{n,20}] (* or *) LinearRecurrence[{31,-155,125},{4,144,3844},20] (* _Harvey P. Dale_, Dec 06 2014 *)
%o A060870 (PARI) a(n) = { (5^n - 1)^2 / 4 } \\ _Harry J. Smith_, Jul 13 2009
%Y A060870 Cf. A060720.
%K A060870 nonn,easy
%O A060870 1,1
%A A060870 Ahmed Fares (ahmedfares(AT)my-deja.com), May 04 2001
%E A060870 More terms from Larry Reeves (larryr(AT)acm.org), May 07 2001