A280777 Denominators of coefficients in asymptotic expansion of C_n (number of connected chord diagrams, A000699).

1, 2, 8, 16, 128, 1280, 3072, 215040, 3440640, 2293760, 137625600, 201850880, 72666316800, 1889324236800, 52901078630400, 176336928768000, 135426761293824, 191854578499584000, 1593868805996544000, 787371190162292736000, 31494847606491709440000, 29395191099392262144000

Offset: 0

Author

N. J. A. Sloane, Jan 19 2017

Keywords

• nonn
• frac

Examples

			Coefficients are 1, -5/2, -43/8, -579/16, -44477/128, -5326191/1280, -180306541/3072, ...
		

Links

• Gheorghe Coserea, Table of n, a(n) for n = 0..101
• Michael Borinsky, Generating asymptotics for factorially divergent sequences, arXiv preprint arXiv:1603.01236 [math.CO], 2016.

Crossrefs

Cf. A000699, A280775, A111111, A280776, A280778, A280779, A280780, A280781.

Programs

PARI

A000699_seq(N) = {
  my(a = vector(N)); a[1] = 1;
  for (n=2, N, a[n] = sum(k=1, n-1, (2*k-1)*a[k]*a[n-k])); a;
};
seq(N) = my(C = 'x*Ser(A000699_seq(N))); Vec(x*exp(1-(2*C+C^2)/(2*x))/C);
apply(denominator, seq(22)) \\ Gheorghe Coserea, Jan 22 2017

Extensions

More terms from Gheorghe Coserea, Jan 22 2017