|
| |
|
|
A143240
|
|
Expansion of Product_{k>0} (1 - x^(3*k)) / (1 - x^(3*k - 1)).
|
|
0
| |
|
|
1, 0, 1, -1, 1, 0, 0, 0, 0, 0, 1, -1, 1, -1, 0, 1, 0, 0, 0, -1, 1, 0, 0, 0, 0, 0, 1, -1, 0, 0, 0, 0, 1, -1, 1, 0, -1, 1, -1, 0, 1, -1, 1, 0, 0, 0, 0, -1, 1, 0, 0, 0, 0, -1, 1, 0, 0, 1, -1, 0, 1, -1, 0, 0, -1, 1, 1, -1, 1, -1, 0, 1, 0, -1, 1, -1, 0, 1, -1, 0, 1, -1, 1, 0, -1, 1, 0, -1, 1, 0, 0, 0, 0, -1, 1, 0, -1, 1, -1, 0, 2, -1, 0, 1, -1
(list; graph; refs; listen; history; internal format)
|
|
|
|
OFFSET
| 0,101
|
|
|
COMMENTS
| |a(n)|<2 if n<100, |a(n)|<3 if n<175.
|
|
|
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
| Sequence in context: A072175 A092147 A175560 * A153659 A016102 A083905
Adjacent sequences: A143237 A143238 A143239 * A143241 A143242 A143243
|
|
|
KEYWORD
| sign
|
|
|
AUTHOR
| Michael Somos, Aug 01 2008
|
| |
|
|
