OFFSET
1,2
LINKS
FORMULA
Prod_{k=1}^{n} (q^k - 1) / (q - 1).
a(1) = 1, a(n) = ((-7)^n - 1)*a(n-1)/(-8). - Vincenzo Librandi, Oct 26 2012
MATHEMATICA
RecurrenceTable[{a[1]==1, a[n]==(((-7)^n - 1) * a[n-1])/(-8)}, a, {n, 15}] (* Vincenzo Librandi, Oct 26 2012 *)
PROG
(Magma) [n le 1 select 1 else ((-7)^n - 1)*Self(n-1)/(-8): n in [1..13]]; // Vincenzo Librandi, Oct 26 2012
CROSSREFS
KEYWORD
sign,easy
AUTHOR
STATUS
approved