OFFSET
0,1
REFERENCES
R. C. Mullin, E. Nemeth and P. J. Schellenberg, The enumeration of almost cubic maps, pp. 281-295 in Proceedings of the Louisiana Conference on Combinatorics, Graph Theory and Computer Science. Vol. 1, edited R. C. Mullin et al., 1970.
N. J. A. Sloane, A Handbook of Integer Sequences, Academic Press, 1973 (includes this sequence).
N. J. A. Sloane and Simon Plouffe, The Encyclopedia of Integer Sequences, Academic Press, 1995 (includes this sequence).
LINKS
T. D. Noe, Table of n, a(n) for n = 0..200
Milan Janjić, Pascal Matrices and Restricted Words, J. Int. Seq., Vol. 21 (2018), Article 18.5.2.
FORMULA
G.f.: 4*(1-4x)^(-3/2).
a(n) = 1/J(n) where J(n) = Integral_{t=0..Pi/4} (cos(t)^2 - 1/2)^(2n+1). - Benoit Cloitre, Oct 17 2006
MAPLE
seq(2*n*binomial(2*n, n), n=1..23); # Zerinvary Lajos, Dec 14 2007
MATHEMATICA
Table[4*(2*n + 1)!/n!^2, {n, 0, 20}] (* T. D. Noe, Aug 30 2012 *)
PROG
(PARI) a(n)=if(n<0, 0, 4*(2*n+1)!/n!^2)
CROSSREFS
KEYWORD
nonn
AUTHOR
EXTENSIONS
Simpler description from Travis Kowalski (tkowalski(AT)coloradocollege.edu), Mar 20 2003
STATUS
approved