OFFSET
1,2
LINKS
Michael De Vlieger, Table of n, a(n) for n = 1..833
W. Lang, On generalizations of Stirling number triangles, J. Integer Seqs., Vol. 3 (2000), #00.2.4.
Elżbieta Liszewska, Wojciech Młotkowski, Some relatives of the Catalan sequence, arXiv:1907.10725 [math.CO], 2019.
FORMULA
a(n) = 4^(n-1)*A007696(n)/n!, A007696(n)=(4*n-3)(!^4) := product(4*j-3, j=1..n), n >= 1; G.f. (-1+(1-16*x)^(-1/4))/4.
D-finite with recurrence: n*a(n) +4*(-4*n+3)*a(n-1)=0. - R. J. Mathar, Jan 28 2020
MATHEMATICA
Rest[CoefficientList[Series[(-1+(1-16x)^(-1/4))/4, {x, 0, 20}], x]] (* Harvey P. Dale, May 19 2011 *)
CROSSREFS
KEYWORD
easy,nonn
AUTHOR
STATUS
approved