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 A176332 Row sums of triangle A176331. 3
 1, 2, 5, 16, 56, 202, 741, 2752, 10318, 38972, 148070, 565280, 2166646, 8332378, 32136205, 124249856, 481433286, 1868972828, 7267804550, 28304698336, 110383060776, 431000853028, 1684754608210, 6592277745536, 25818887839956 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 COMMENTS Hankel transform is A176333. LINKS FORMULA a(n)=sum{k=0..n, sum{j=0..n, C(j,n-k)*C(j,k)*(-1)^(n-j)}}. Logarithm g.f. atan(x*C(x))=sum(n>0, a(n)/n*x^n), C(x)=(1-sqrt(1-4*x))/(2*x) (A000108) [From Vladimir Kruchinin, Aug 10 2010] Conjecture: 6*n*a(n) +2*(-17*n+10)*a(n-1) +(47*n-60)*a(n-2) +10*(-3*n+5)*a(n-3) +4*(2*n-5)*a(n-4)=0. - R. J. Mathar, Nov 24 2012 MATHEMATICA f[n_] := (-1)^n*Sum[ Binomial[n + k, k] Cos[Pi (n + k)/2], {k, 0, n}]; Array[f, 24, 0] (* Robert G. Wilson v, Apr 02 2012 *) CROSSREFS Sequence in context: A137732 A057973 A102461 * A191241 A052708 A149973 Adjacent sequences:  A176329 A176330 A176331 * A176333 A176334 A176335 KEYWORD easy,nonn AUTHOR Paul Barry, Apr 15 2010 STATUS approved

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