OFFSET
1,2
LINKS
FORMULA
a(n) = product_{k=1..n} ((-3)^k - 1)/(-3 - 1).
a(1) = 1, a(n) = ((-3)^n - 1)*a(n-1)/(-4). - Vincenzo Librandi, Oct 26 2012
MATHEMATICA
RecurrenceTable[{a[1]==1, a[n]==(((-3)^n - 1) * a[n-1])/(-4)}, a, {n, 18}] (* Vincenzo Librandi, Oct 26 2012 *)
PROG
(Magma) [n le 1 select 1 else ((-3)^n - 1)*Self(n-1)/(-4): n in [1..18]]; // Vincenzo Librandi, Oct 26 2012
CROSSREFS
KEYWORD
sign,easy
AUTHOR
STATUS
approved