OFFSET
1,1
LINKS
Harry J. Smith, Table of n, a(n) for n = 1..200
Index entries for linear recurrences with constant coefficients, signature (13,-39,27).
FORMULA
a(n) = 1/2 * (3^n - 1)^2.
G.f.: -2*x*(3*x+1) / ((x-1)*(3*x-1)*(9*x-1)). [Colin Barker, Dec 23 2012]
EXAMPLE
a(2) = 32 because there are 33 (the second element in sequence A060705) singular 2 X 2 matrices over GF(3), that have rank <= 1 of which only the zero matrix has rank zero so a(2) = 33 - 1 = 32.
PROG
(PARI) { for (n=1, 200, write("b060868.txt", n, " ", (3^n - 1)^2 / 2); ) } \\ Harry J. Smith, Jul 13 2009
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
Ahmed Fares (ahmedfares(AT)my-deja.com), May 04 2001
EXTENSIONS
More terms from Jason Earls, May 05 2001
STATUS
approved