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 A070877 Expansion of Product_{k>=1} (1 - 2x^k). 5
 1, -2, -2, 2, 2, 6, -2, 2, -6, -10, -2, -6, -6, 6, 22, -6, 26, 14, 22, -6, -14, -2, -10, -46, -46, -50, -18, 18, -78, 22, 14, 82, 42, 166, 14, 42, 170, 118, 6, 106, -150, -66, -122, -118, -62, -370, -282, -350, -126, -354, -2, -94, 226, -250, 30, 450, 730, 342, 894, 474, 890, 358, 758, 58, 1210, 782, -778, 26, -270, -1250 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 LINKS Seiichi Manyama, Table of n, a(n) for n = 0..10000 (terms 0..1000 from Giovanni Resta) EXAMPLE G.f. = 1 - 2*x - 2*x^2 + 2*x^3 + 2*x^4 + 6*x^5 - 2*x^6 + 2*x^7 - 6*x^8 - 10*x^9 + ... MATHEMATICA CoefficientList[ Series[ Product[(1 - 2t^k), {k, 1, 80}], {t, 0, 80}], t] a[ n_] := SeriesCoefficient[ -QPochhammer[2, x], {x, 0, n}]; (* Michael Somos, Mar 11 2014 *) PROG (PARI) N=66; q='q+O('q^N); Vec(sum(n=0, N, (-2)^n*q^(n*(n+1)/2) / prod(k=1, n, 1-q^k ) )) \\ Joerg Arndt, Mar 09 2014 (PARI) N=66; q='q+O('q^N); t2=Vec( prod(k=1, N, 1-2*q^k) ) \\ Joerg Arndt, Mar 11 2014 CROSSREFS Cf. A070933, A010815, A032302. Sequence in context: A273258 A073124 A278260 * A156717 A198889 A329814 Adjacent sequences:  A070874 A070875 A070876 * A070878 A070879 A070880 KEYWORD sign AUTHOR Sharon Sela (sharonsela(AT)hotmail.com), May 24 2002 EXTENSIONS Edited by Robert G. Wilson v, May 26 2002 Corrected by Vincenzo Librandi, Mar 11 2014 STATUS approved

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Last modified August 10 02:28 EDT 2020. Contains 336367 sequences. (Running on oeis4.)