1,6

L. Comtet, Advanced Combinatorics, Reidel, 1974, p. 49.

D. Dumont, Interpretations combinatoires des nombres de Genocchi, Duke Math. J., 41 (1974), 305-318.

A. Fletcher, J. C. P. Miller, L. Rosenhead and L. J. Comrie, An Index of Mathematical Tables. Vols. 1 and 2, 2nd ed., Blackwell, Oxford and Addison-Wesley, Reading, MA, 1962, Vol. 1, p. 73.

R. L. Graham, D. E. Knuth and O. Patashnik, Concrete Mathematics. Addison-Wesley, Reading, MA, 1990, p. 528.

G. Kreweras, Sur les permutations compte'es par les nombres de Genocchi..., Europ. J. Comb., vol. 18, pp. 49-58, 1997.

R. P. Stanley, Enumerative Combinatorics, Cambridge, Vol. 2, 1999; see Problem 5.8.

H. M. Terrill and E. M. Terrill, Tables of numbers related to the tangent coefficients, J. Franklin Inst., 239 (1945), 66-67.

R. C. Archibald, Review of Terrill-Terrill paper, Math. Comp., 1 (1945), pp. 385-386.

Kwang-Wu Chen, An Interesting Lemma for Regular C-fractions, J. Integer Seqs., Vol. 6, 2003.

E.g.f.: 2x/(exp(x)+1).

a(n) = 2*(1-2^n)*B_n (B = Bernoulli numbers) - Benoit Cloitre (benoit7848c(AT)orange.fr), Oct 26 2003

2x/(exp(x)+1) = x + Sum_{n>0} x^(2n)*G_{2n}/(2n)!.

a(n) = Sum_{k=0^(n-1)} binomial(n,k) 2^k B(k). [From Peter Luschny (peter(AT)luschny.de), Apr 30 2009]

a := n -> n*euler(n-1, 0); [From Peter Luschny (peter(AT)luschny.de), Jul 13 2009]

(PARI) a(n)=if(n<0, 0, n!*polcoeff( 2*x/(1+exp(x+x*O(x^n))), n)) /* Michael Somos Jul 23 2005 */

A001469 is the main entry for this sequence.

Sequence in context: A013494 A038122 A143779 this_sequence A024040 A009759 A127187

Adjacent sequences: A036965 A036966 A036967 this_sequence A036969 A036970 A036971

sign,easy,nice

N. J. A. Sloane (njas(AT)research.att.com).