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 A189053 Expansion of d/dx log(1/(1-x/sqrt(1-4*x^2))). 1
 1, 1, 7, 9, 41, 61, 225, 369, 1195, 2101, 6227, 11529, 32059, 61741, 163727, 325089, 831505, 1690981, 4206145, 8717049, 21215481, 44633821, 106782837, 227363409, 536618341, 1153594261, 2693492305, 5835080169, 13507578125, 29443836301 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,3 LINKS Vincenzo Librandi, Table of n, a(n) for n = 0..100 FORMULA G.f. sqrt(1-4*x^2)/(16*x^4+sqrt(1-4*x^2)*(4*x^3-x)-8*x^2+1), a(n)=n*sum(k=1..n, (binomial((n-2)/2,(n-k)/2)*2^(n-k-1)*((-1)^(n-k)+1))/k); PROG (Maxima) a(n):=n*sum((binomial((n-2)/2, (n-k)/2)*2^(n-k-1)*((-1)^(n-k)+1))/k, k, 1, n); (Pari) x='x+O('x^66); /* that many terms */ Vec(deriv(log(1/(1-x/sqrt(1-4*x^2))))) /* show terms */ /* Joerg Arndt, Apr 16 2011 */ CROSSREFS Sequence in context: A140787 A032695 A007449 * A067649 A025631 A038275 Adjacent sequences:  A189050 A189051 A189052 * A189054 A189055 A189056 KEYWORD nonn AUTHOR Vladimir Kruchinin, Apr 16 2011 STATUS approved

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