OFFSET
0,2
COMMENTS
{abs(a(n))} has e.g.f. sinh(sinh(sinh(x))) (odd powers only). - Jianing Song, Oct 25 2023
REFERENCES
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
Vincenzo Librandi, Table of n, a(n) for n = 0..100
FORMULA
a(k) : =sum(j=0..k, (sum(m=j..k, (2^(-2*j-2*m)*(sum(i=0..(2*j+1)/2, (2*i-2*j-1)^(2*m+1)*(-1)^(i)*binomial(2*j+1,i)))*sum(i=0..(2*m+1)/2, (2*i-2*m-1)^(2*k+1)*binomial(2*m+1,i)*(-1)^(k-i)))/(2*m+1)!))/(2*j+1)!); [Vladimir Kruchinin, Jun 10 2011]
MATHEMATICA
With[{nn = 50}, Take[CoefficientList[Series[Sin[Sin[Sin[x]]], {x, 0, nn}], x] Range[0, nn - 1]!, {2, -1, 2}]] (* Vincenzo Librandi, Apr 11 2014 *)
PROG
(Maxima)
a(k):=sum((sum((2^(-2*j-2*m)*(sum((2*i-2*j-1)^(2*m+1)*(-1)^(i)*binomial(2*j+1, i), i, 0, (2*j+1)/2))*sum((2*i-2*m-1)^(2*k+1)*binomial(2*m+1, i)*(-1)^(k-i), i, 0, (2*m+1)/2))/(2*m+1)!, m, j, k))/(2*j+1)!, j, 0, k). /* Vladimir Kruchinin, Jun 10 2011 */
CROSSREFS
KEYWORD
sign
AUTHOR
STATUS
approved