OFFSET
0,2
FORMULA
a(n) = Sum_{r=1..n} r*Product_{j=0..r-1} (q^n-q^j)^2/(q^r-q^j) with q=3.
PROG
(PARI) a(n)=sum(r=1, n, r*prod(j=0, (r-1), (3^n-3^j)^2/(3^r-3^j)))
CROSSREFS
KEYWORD
nonn
AUTHOR
Yuval Dekel (dekelyuval(AT)hotmail.com), Aug 26 2003
EXTENSIONS
More terms from Benoit Cloitre, Aug 27 2003
a(10) from Andrew Howroyd, Jul 08 2018
STATUS
approved