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 A217334 G.f.: exp( Sum_{n>=1} (2*sigma(n^2) - sigma(n)^2 - sigma(n,2))/2 * x^n/n ). 1
 1, 0, 0, 0, -1, 0, -1, 0, -3, -1, 0, 0, -4, 1, 3, 0, 4, 3, 1, 1, 16, 4, 10, 0, 15, -4, 6, 0, 14, -15, -11, -9, -29, -5, -56, -14, -56, -24, -101, 10, -140, -8, -25, 18, -101, 27, 7, 50, 91, 128, 222, 29, 300, 207, 516, 119, 614, 73, 762, 115, 510, 89, 614, -280 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,9 COMMENTS The number of contiguous signs appear to increase (roughly) in proportion to the square-root of the number of terms. LINKS Paul D. Hanna, Table of n, a(n) for n = 0..1000 EXAMPLE G.f.: A(x) = 1 - x^4 - x^6 - 3*x^8 - x^9 - 4*x^12 + x^13 + 3*x^14 + 4*x^16 +... where log(A(x)) = -4*x^4/4 - 6*x^6/6 - 28*x^8/8 - 9*x^9/9 - 10*x^10/10 - 94*x^12/12 - 14*x^14/14 - 15*x^15/15 - 140*x^16/16 +... PROG (PARI) {a(n)=polcoeff(exp(sum(m=1, n, (sigma(m^2)-sigma(m)^2/2-sigma(m, 2)/2)*x^m/m)+x*O(x^n)), n)} for(n=0, 70, print1(a(n), ", ")) CROSSREFS Sequence in context: A059202 A244963 A144452 * A369455 A353859 A058865 Adjacent sequences: A217331 A217332 A217333 * A217335 A217336 A217337 KEYWORD sign AUTHOR Paul D. Hanna, Sep 30 2012 STATUS approved

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Last modified May 20 08:05 EDT 2024. Contains 372703 sequences. (Running on oeis4.)