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 A161519 Expansion of Sum_{n >= 1} (-1)^nq^(n^2+n)(1-q^2)(1-q^4)...(1-q^(2n-2))/((1+q)(1+q^2)...(1+q^(2n))). 0
 -1, 1, 0, 0, 0, 0, -1, 0, 0, 2, -1, 0, 0, 0, 0, 0, -1, 0, 0, 0, 0, 2, 0, 0, -2, 1, 0, 0, 0, 0, -1, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, -2, 0, 0, 2, -1, 0, -1, 0, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, -2, 0, 0, 0, 0, 2, -1, 0, -2, 1, 0, 0, 0, 0, 0, 0, 0, 2, 0, 0, 0, 0, 0, 0, 0, 0, -2, 0, 0, 0, 0, 0, -1, 2 (list; graph; refs; listen; history; text; internal format)
 OFFSET 2,10 COMMENTS -(-1)^n*a(n) is the number of inequivalent elements of norm -n in Z[sqrt{3}]. LINKS Jeremy Lovejoy, Overpartitions and real quadratic fields, J. Number Theory, 106 (2004), 178-186. CROSSREFS Sequence in context: A037858 A037876 A263774 * A286561 A068101 A094263 Adjacent sequences:  A161516 A161517 A161518 * A161520 A161521 A161522 KEYWORD sign AUTHOR Jeremy Lovejoy, Jun 12 2009 STATUS approved

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Last modified August 18 13:46 EDT 2019. Contains 326100 sequences. (Running on oeis4.)