The OEIS is supported by the many generous donors to the OEIS Foundation.

 Hints (Greetings from The On-Line Encyclopedia of Integer Sequences!)
 A143240 Expansion of Product_{k>0} (1 - x^(3*k)) / (1 - x^(3*k - 1)). 2
 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; text; internal format)
 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 Cf. A113706. Sequence in context: A092147 A208134 A175560 * A363338 A290260 A304273 Adjacent sequences: A143237 A143238 A143239 * A143241 A143242 A143243 KEYWORD sign AUTHOR Michael Somos, Aug 01 2008 STATUS approved

Lookup | Welcome | Wiki | Register | Music | Plot 2 | Demos | Index | Browse | More | WebCam
Contribute new seq. or comment | Format | Style Sheet | Transforms | Superseeker | Recents
The OEIS Community | Maintained by The OEIS Foundation Inc.

Last modified September 28 05:44 EDT 2023. Contains 365724 sequences. (Running on oeis4.)