OFFSET
0,101
COMMENTS
|a(n)|<2 if n<100, |a(n)|<3 if n<175.
LINKS
Seiichi Manyama, Table of n, a(n) for n = 0..10000
FORMULA
Euler transform of period 3 sequence [ 0, 1, -1, ...].
G.f.: Product_{k>0} (1 - x^(3*k)) / (1 - x^(3*k - 1)).
EXAMPLE
1 + q^2 - q^3 + q^4 + q^10 - q^11 + q^12 - q^13 + q^15 - q^19 + q^20 + ...
PROG
(PARI) {a(n) = if( n<0, 0, polcoeff( prod(k=1, (n+1)\3, (1 - x^(3*k)) / (1 - x^(3*k - 1)), 1 + x * O(x^n)), n))}
CROSSREFS
KEYWORD
sign
AUTHOR
Michael Somos, Aug 01 2008
STATUS
approved