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 A227830 Denominators of coefficients in expansion of x/(exp(x)-1). 4
 1, 2, 12, 1, 720, 1, 30240, 1, 1209600, 1, 47900160, 1, 1307674368000, 1, 74724249600, 1, 10670622842880000, 1, 5109094217170944000, 1, 802857662698291200000, 1, 14101100039391805440000, 1, 1693824136731743669452800000, 1, 186134520519971831808000000, 1, 37893265687455865519472640000000, 1, 759790291646040068357842010112000000, 1 (list; graph; refs; listen; history; text; internal format)
 OFFSET 0,2 REFERENCES M. Kauers and P. Paule, The Concrete Tetrahedron, Springer 2011, p. 23. LINKS Table of n, a(n) for n=0..31. FORMULA Recurrence: R(0) = 1 and R(n) = - Sum_{k=0..n-1} R(k)/(n-k+1)! for n>=1. Then a(n) = denominator(R(n)). - Peter Luschny, Jul 30 2015 EXAMPLE 1, -1/2, 1/12, 0, -1/720, 0, 1/30240, 0, -1/1209600, 0, 1/47900160, 0, -691/1307674368000, 0, 1/74724249600, 0, ... MATHEMATICA Denominator[ CoefficientList[ Series[x/(1 - E^-x), {x, 0, 26}], x]] (* Robert G. Wilson v, Dec 29 2016 *) PROG (Sage) @cached_function def R(n): return -sum(R(k)/factorial(n-k+1) for k in (0..n-1)) if n>0 else 1 print([R(n).denominator() for n in (0..31)]) # Peter Luschny, Jul 30 2015 CROSSREFS For numerators see A120082. Cf. A060054, A060055. Sequence in context: A221075 A211798 A075180 * A299521 A167164 A277265 Adjacent sequences: A227827 A227828 A227829 * A227831 A227832 A227833 KEYWORD nonn,frac AUTHOR N. J. A. Sloane, Aug 01 2013 STATUS approved

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Last modified April 22 17:45 EDT 2024. Contains 371906 sequences. (Running on oeis4.)