OFFSET
0,3
LINKS
FORMULA
a(n) = Product_{k=1..n} (q^k - 1) / (q - 1) with q=4.
a(0) = 1, a(n) = (4^n-1)*a(n-1)/3. - Vincenzo Librandi, Oct 27 2012
MATHEMATICA
RecurrenceTable[{a[1]==1, a[n]==((4^n - 1) * a[n-1])/3}, a, {n, 15}] (* Vincenzo Librandi, Oct 27 2012 *)
Table[QFactorial[n, 4], {n, 15}] (* Bruno Berselli, Aug 14 2013 *)
PROG
(Magma) [n le 1 select 1 else (4^n-1)*Self(n-1)/3: n in [1..15]]; // Vincenzo Librandi, Oct 22 2012
CROSSREFS
KEYWORD
nonn,easy
AUTHOR
EXTENSIONS
a(0)=1 prepended by Alois P. Heinz, Sep 08 2021
STATUS
approved